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PROM A RECENT PHOTOGRAPH 



THE ELEMENTS 



OF 



PHYSICAL G-EOG-RAPHY, 



FOR THE USE OF 



Schools, Academies, and Colleges. 




BY 



EDWIN J (^HOUSTON, A.M., Ph.D., 



EMERITUS PROFESSOR OF PHYSICAL GEOGRAPHY AND NATURAL PHILOSOPHY IN THE CENTRAL 

HIGH SCHOOL OF PHILADELPHIA; PROFESSOR OF PHYSICS IN THE FRANKLIN 

INSTITUTE OF THE STATE OF PENNSYLVANIA. 



REVISED EDITION. 



1895 




1 



SffawyFTs 



philadelphia: 
Published by Eldredge & Brother. 

No. 17 North Seventh Street. 
1895. 



\ 



••o£o»- 



Entered, according to Act of Congress, in the year 1891, by 

ELDEEDGE & BROTHER, 
in the Office of the Librarian of Congress, at Washington. 



■•0^>0»' 



Copyright, 189S. 



"Westcott & Thomson, 
Electrotypers, PhUada. 



The George S. Ferguson Co., 
Printers, PhUada. 




Preface 

TO THE ORIGINAL EDITION. 



TN the preparation of this work, an endeavor has been made to supply a concise yet comprehensive 
-^ text-book, suited to the wants of a majority of our schools. 

The Author, in the course of his teaching, has experienced the need of a work in which unneces- 
sary details should be suppressed, and certain subjects added, which, though usually omitted in works 
on Physical Geography, seem, in his judgment, to belong properly to the science. The variety of 
topics necessarily included under the head of Physical Geography renders it almost impossible to 
cover the. entire ground of the ordinary text-books during the time which most schools are able to 
devote to the study, and the feeling of incompleted work thus impressed on the mind of both teacher 
and scholar is of the most discouraging nature. 

To remove these difficulties, the Author, during the past few years, has arranged for his own 
students a course of study, which, with a few modifications, he has at last put into book form, thinking 
that it may prove beneficial to others. 

The division of the text into large and small print has been made with a view of meeting the 
wants of different grades of schools, the large type containing only the more important statements, and 
the small type being especially designed for the use of the teacher and the advanced student. The 
maps have been carefully drawn by the Author according to the standard works and the latest 
authorities. Neither time nor expense has been spared to insure accuracy of detail and clearness 
of delineation. 

Throughout the work no pains have been spared to insure strict accuracy of statement. Clearness 
and conciseness have been particularly aimed at; for" which reason the names of authorities for state- 
ments which are now generally credited have been purposely omitted. 

The Author has not hesitated to draw information from all the standard works on Geography, 
Physics, Geology, Astronomy, and other allied sciences ; and in the compilation of the Pronouncing 
Vocabulary he acknowledges his indebtedness to Lippincott's Gazetteer of the World. 

Acknowledgments are due to Mr. William M. Spackman, of Philadelphia, and Prof. Elihu 
Thomson, of the Central High School, for critical review of the manuscript. Also to Mr. M. Benja- 
min Snyder, of the Central High School, for revision of the proof-sheets of the chapter on Mathe- 
matical Geography. E. J. H. 

Central High School, Philadelphia, Pa. 

iii 




Preface 



TO THE REVISED EDITION. 



oXXc 



rnHE marked progress which has been made in most of the departments of science embraced 

in the study of Physical Geography since the issue of the original edition of "The 
Elements of Physical Geography" has rendered the preparation of a revised edition a matter 
of necessity. 

The study of Physical Geography, including as it does not only the crust of the earth and 
its heated interior, but also the distribution of its land, water, air, plants, and animals, includes, 
in its range, a great variety of topics, and necessitates for its proper elucidation many branches 
of science. Some knowledge of the elementary principles of these sciences is necessary to the 
proper study of Physical Geography. The number of such principles is great, and the temptation 
naturally exists to encumber even an elementary text-book -with such an abundance of leading 
principles as to render it either incomprehensible, or too extended for actual use in the school- 
room. 

The author has endeavored in the revised edition to avoid undue multiplicity either of ele- 
mentary principles or unimportant details. His object has been to develop forcibly the close inter- 
dependence of the inanimate features of the earth's surface, the land, water, and air, with its 
animate features, its flora, and fauna, and to show the marked influence which all of these exert 
on the development of the human race, and, therefore, on history itself. 

Kecognizing, from his standpoint of a teacher, the inadvisability of crowding a book with 
new matter simply because it is new, the author has carefully avoided the introduction of new 
theories unless they have been generally accepted by the best authorities. Old theories are in all 
cases given the preference of new ones, unless the latter bear the stamp of general approval. 
At the same time the results of recent investigations have been freely given in all cases where 
they have been considered sufficiently authoritative. 



PREFACE. 



In order to avoid confusing the mind of the student, controversial matters have been carefully 
avoided. When, however, opinion on any subject is fairly divided, a brief statement is made of the 
differing views. 

The favorable reception accorded by the teaching profession to the earlier editions of the book, 
and the flattering increase in the number of schools using it, have satisfied the author of the 
inadvisability of changing, to any considerable extent, the order of sequence of topics discussed, or 
the general manner of explanation therein adopted. 

In the preparation of the revised edition the author has freely consulted the latest standard 
authorities in the many sciences represented. 

The maps have all been re-drawn according to the best authorities, and are printed and colored 
by processes that in point of clearness and beauty leave little room for improvement. 

EDWIN J. HOUSTON. 



Central High School, 

Philadelphia, Pa. 



NOTE. 



The first chapter of this book is intended mainly for reference, containing as it does, an abstract 
of the elementary principles of Mathematical Geography, with which most pupils beginning the study 
of Physical Geography are familiar. In many schools in which the book is used, it is customary 
to begin the formal study of the book with the Syllabus, page SI, which presents a comprehensive 
review of the chapter, and in practice and results this plan has proved satisfactory. 





Contents. 



INTRODUCTORY 



PAGE 

. 9 



PART I. 

THE EARTH AS A PLANET. 

CHAPTER 

I. Mathematical Geography 10 

Syllabus 21 

Beview Questions 21 



PART II. 

THE LAND. 

Section I. 

THE INSIDE OF THE EARTH. 

I. The Heated Inteeioe 

II. Volcanoes 

III. Earthquakes 

Syllabus 

Beview and Map Questions 



,22 

23 

28 

.31 

,32 



Section II. 

THE OUTSIDE OF THE EARTH. 

I. The Crust of the Earth 33 

II. Distribution of the Land Areas ... 37 

III. Islands 39 

IV. Belief Forms of the Land 42 

V. Belief Forms of the Continents ... 45 

Syllabus 54 

Eeyiew Questions 55 

Map Questions 56 

PART III. 

THE WATER. 

Section I. 

CONTINENTAL. WATERS. 

L Physical Properties of Water .... 57 
JL Drainage 59 



CHAPTER PAGE 

III. Bivers 63 

IV. Transporting Power of Biyers ... 65 
V. Drainage Systems 67 

VI. Lakes 69 

Syllabus 71 

Beview and Map Questions 72 

Section II. 

OCEANIC WATERS. 

I. The Ocean 73 

II. Oceanic Movements 75 

III. Ocean Currents 79 

Syllabus 83 

Beview and Map Questions 84 

PART IV. 

THE ATMOSPHERE. 

Section I. 

THE ATMOSPHERE. 

I. General Properties of the Atmosphere 85 

II. Climate 87 

III. The Winds 90 

IV. Storms 96 

Syllabus 98 

Beview Questions 99 

Map Questions 100 



Section II. 

MOISTURE OF THE ATMOSPHERE. 

I. Precipitation of Moisture 101 

II. Hail, Snow, and Glaciers 107 

III. Electrical and Optical Phenomena . 110 

Syllabus 115 

Beview Questions 116 

Map Questions 117 



CONTENTS. 



PART V. 

PLANT LIFE, ANIMAL LIFE, AND 
MINERALS. 

Section I. 

PLANT LIFE. 

CHAPTER PAGE 

I. Plant Geography 118 

II. Cultivated Plants 124 

Syllabus 127 

Review and Map Questions 128 

Section II. 

ANIMAL LIFE. 

I. Zoological Geography 129 

II. Characteristic Fauna of the Conti- 
nents 133 

III. The Distribution of the Human Pace 135 

Syllabus 138 

Review Questions 139 

Map Questions 140 

Section III. 

MINERALS. 

I. Minerals 141 

Syllabus 144 

Review Questions 144 



PART VI. 

THE PHYSICAL FEATURES OF THE 
UNITED STATES. 

CHAPTEK PAGE 

I. Surface Structure 146 

II. Meteorology 150 

III. Vegetable and Animal Life 155 

IV. Agricultural and Mineral Produc- 

tions 156 

V. Alaska 160 

Syllabus 161 

Review Questions 162 

Map Questions 163 

GENERAL SYLLABUS 163 

GENERAL REVIEW QUESTIONS .... 166 

GENERAL MAP QUESTIONS 167 

PRONOUNCING VOCABULARY 170 

BRIEF ETYMOLOGICAL VOCABULARY 173 

STATISTICAL TABLES 174 

INDEX 176 



INDEX TO THE MAPS. 

*o>e<oo 

PAGE 

MAP OF VOLCANOES AND REGIONS OF EARTHQUAKES 26 

MAP OF OCEANIC AREAS AND RIVER-SYSTEMS 68 

MAP OF THE OCEAN CURRENTS 81 

MAP OF THE ISOTHERMAL LINES 88 

MAP OF THE WINDS, RAIN, AND OCEAN ROUTES 94 

MAP SHOWING THE DISTRIBUTION OF VEGETATION 121 

MAP SHOWING THE DISTRIBUTION OF ANIMALS 131 

MAP SHOWING THE DISTRIBUTION OF THE RACES OF MEN 136 

PHYSICAL MAP OF THE UNITED STATES 145 

MAP SHOWING THE MEAN TRACKS OF STORM-CENTRES, AREAS OF LOW BAROM- 
ETER, WEATHER SIGNALS, AND STORM SIGNALS 152 





Physical Geogkaphy. 



Introductory. 



1. Geography is a description of the earth. 

The earth may be considered in three different 
ways: 

(1.) In its relations to the solar system ; 

(2.) In its relations to government and society; 

(3.) In its relations to nature. 

Hence arise three distinct branches of geog- 
raphy — Mathematical, Political, and Physical. 

2. Mathematical Geography treats of the earth 
in its relations to the solar system. 

Mathematical Geography forms the true basis for 
accurate geographical study, since by the view we thus 
obtain of the earth in its relations to the other members 
of the solar system, we are enabled to form clearer concep- 
tions of the laws which govern terrestrial phenomena. 
Here we learn the location of the earth in space, its size, 
form, and movements, its division by imaginary lines, and 
the methods of representing portions of its surface on maps. 

3. Political Geography treats of the earth in 
its relations to the governments and societies of 

2 



men, of the manner of life of a people, and of 
their civilization and government. 

4. Physical Geography treats of the earth in 
its relations to nature and to the natural laws by 
which it is governed. It treats especially of the 
systematic distribution of all animate and inani- 
mate objects found on the earth's surface. It not 
only tells of their presence in a given locality, 
but it also endeavors to discover the causes and 
results of their existence. 

Physical Geography, therefore, treats of the 
distribution of six classes of objects — Land, Water, 
Air, Plants, Animals, and Minerals. 

Geography deals with the inside as well as with the out- 
side of the earth. It encroaches here on the province of 
geology. Both treat of the earth : geography mainly with 
the earth's present condition ; geology with its condition 
both in the past and present, though mainly during the past. 

Some authors make physical geography a branch of geol- 
ogy, and call it physiographic geology, but we prefer the 
word "physical," or as the etymology would make it, 
"natural" geography. 

9 



Part I. 

THE EARTH AS A PLANET. 




Fig. 1. The Earth ia Space. 

CHAPTER I. 

Mathematical Geography. 

5. The Earth moves through empty space 
around the sun. The old idea of the earth 
resting on, or being supported by something, is 
erroneous. The earth rests on nothing. 

A book or other inanimate object placed on a 
support will remain at rest until something or 
somebody moves it, because it has no power of 
self-motion. This property is called inertia. 

Inertia is not confined to bodies at rest. If 
the book be thrown up through the air, it ought 
to keep on moving upward for ever, because it 
has no more power to stop moving than to begin 
to move. We know, however, that in reality it 
stops very soon, and falls to the earth ; because — 

(1.) The earth draws or attracts it ; 

(2.) The falling body gives some of its motion 
to the air through which it moves. 

Were the book thrown in any direction through 
the empty space in which the stars move, it would 
continue moving in that direction for ever, unless 
it came near enough to some other body which 
would attract it and cause it to change its motion. 

Our earth moves through empty space on ac- 
count of its inertia, and must continue so moving 
for eternities. There are ample reasons for believ- 

10 



ing that all heavenly bodies continue their mo- 
tion solely on account of their inertia. The curved 
paths in which the earth and the other planets 
move are resultant paths produced in a manner 
that will be explained hereafter. 

Space is not absolutely empty, but is everywhere filled 
with a very tenuous substance called ether, which trans- 
mits to us the light and heat of the heavenly bodies. 
Wherever the telescope reveals the presence of stars we 
must believe the ether also extends. 

6. The Stars. — The innumerable points of light 
that dot the skies are immense balls of matter 
which, like our earth, are moving through empty 
space. Most of them are heated so intensely that 
they give off heat and light in all directions. 
They are so far from the earth that they would 
not be visible but for their immense size. Beyond 
them are other balls, also self-luminous, but too 
far off to be visible except through a telescope. 
Beyond these, again, we have reason to believe 
that there are still others. Tliese balls of matter 
are called stars. 

All the heavenly bodies, however, do not shine 
by their own light. A few — those nearest the 
earth- — shine by reflecting the light of the sun. 
These are called planets, and move with the earth 
around the sun. 

7. The Solar System comprises the sun, eight 
large bodies called planets, and, as far as now 
known, three hundred and eighty-four smaller 
bodies called planetoids or asteroids, besides nu- 
merous comets and meteors. Some of the planets 
have bodies called moons or satellites moving 
around them. These also belong to the solar 
system. 

Fig. 2 represents the solar system. In the 
centre is the sun. , The circles drawn around 
the sun show the paths or orbits of the planets. 
These orbits are represented as circular, but in 
reality they are slightly flattened or elliptical. 
The elongated orbits mark the paths of the comets. 



MATHEMATICAL GEOGRAPHY. 



11 




Fig. 2. The Solar System. 



The drawing shows the order of the planets from 
the sun their common centre, together with the 
satellites or moons of some of the planets, and 
the rings of Saturn. 

8. Names of the Planets. — The planets, named 
in their regular order from the sun, beginning 
with the nearest, are as follows — viz. : Mercury, 
Venus, Earth, Mars, Jupiter, Saturn, Uranus, and 
Neptune. The first four — Mercury, Venus, Earth, 
and Mars — are comparatively small ; the second 
four — Jupiter, Saturn, Uranus, and Neptune — are 
very large, Jupiter being nearly fourteen hun- 



dred times larger than the earth. The initial 
letters of the last three planets, Saturn, Uranus, 
and Neptune, taken in their order from the sun : 
s, u, and n — spell the name of their common 
centre. 

s Mercury has a mean or average distance of 36,000,000 
of miles from the sun ; Venus, 67,200,000 ; Earth, 92,900,000 ; 
and Mars, 141,500,000. 

Jupiter is 483,000,000: Saturn, 886,000,000; Uranus, 
1,781,900,000; Neptune, 2,791,600,000. The asteroids move 
around the sun in the space between the orbits of Mars and 
Jupiter. 

* Calculated in round numbers for the mean solar distance of 
92,897,000 miles. 



12 



PHYSICAL GEOGKAPHY. 



It is difficult to obtain clear conceptions of distances that 
are represented by millions of miles. We may learn the 
numbers, but in general they convey no definite ideas. 
Should a man travel forty times around the earth at the 
equator, he would only have gone over about 1,000,000 
miles. Now, Mercury, the nearest of the planets, is thirty- 
six times farther from the sun than the entire distance the 
man would have travelled, while Neptune is nearly three 
thousand times the distance he would have travelled. 

9. The Satellites. — A satellite is a body that 
revolves around another body: the planets are 
satellites of the sun ; the moon is a satellite of 
the earth. Mars has two moons. So far as is 
known, neither Mercury nor Venus has a satel- 
lite. All the planets whose orbits are beyond the 
orbit of the earth have moons : Jupiter has five, 
Uranus six, Saturn eight, and Neptune one. Be- 
sides its moons, Saturn has a number of curious 
ring-like accumulations of separate solid or liquid 
particles revolving around it. The earth's moon 
is about 240,000 miles from the earth. Its vol- 
ume is about one-forty-ninth that of the earth's. 

10. The Sun is the great central body of the 
solar system. Around it move the planets with 
their satellites, receiving their light and heat 
from it. The sun is a huge heated mass about 
1,300,000 times the size of the earth. Its diam- 
eter is about 866,500 miles. It appears the 
largest self-luminous body in the heavens because 
it is comparatively near the earth. Many stars 
which appear as mere dots of light are much 
larger than the sun. 

The sun is a body heated to luminosity, and gives out or 
emits light and heat like any other highly-heated body. 
If no causes exist to maintain its heat, it will eventu- 
ally cool and fail to emit light. The sun's heat is partly 
kept up by a variety of causes, the principal of which is 
the heat developed by meteoric showers that fall on its 
surface. If a meteor fall toward the sun from inter- 
planetary space, it will reach the surface with enormous 
velocity, and its motion will there be converted into 
heat. Since, however, the increase of the sun's mass so 
necessitated is not confirmed by astronomical observa- 
tions, it is believed that the sun's heat is not being main- 
tained in this way, and that the sun must eventually cool 
— an event, however, so remote in time that the life of the 
solar system may be regarded as practically infinite. 

Size of the Sun. — Were the sun hollow and the earth 
placed at its centre, there would not only be sufficient room 
to enable the moon to revolve at its present actual distance 
around the earth, but it would still, in all parts of its orbit, 
be nearly 200,000 miles below the surface of the sun. 

All the fixed stars are distant suns, and probably have 
worlds like our own moving around them. 

From the enormous distances of the fixed stars, we are 
obliged, in estimating their distances, to use for our unit 
of measurement the velocity of light. Any other common 
unit would be too small. Light moves through space at 
the rate of about 186,000 miles a second, which is over 



11,000,000 miles a minute. Notwithstanding this prodig- 
ious velocity, it would take over three thousand years for 
light to reach the earth from some of the stars that are 
visible to the naked eye. But beyond these stars the tele- 
scope reveals myriads of others, whose number is limited 
only by the power of the instrument. We may conclude 
that the universe is as boundless as space; that is, light 
can never reach its extreme limits. 

11. Cause of the Earth's Revolution. — The earth 
continues its motion through space solely on account of 
its inertia. Its curved path around the sun is a resultant 
caused by the constant action of two forces : one, a pro- 
jectile force probably imparted to it when it began its 
separate existence; the other, the sun's attraction, which 
causes the earth to fall toward the sun. Under the influ- 
ence of the projectile force alone the earth would, in a 
given time, move from a to b (Fig. 3) ; but during this time 

b 




Fig. 3, Cause of the Carved Shape of the Earth's Orbit, 

it has been continually changing its direction by an 
amount equivalent to a direct fall from b to c along b d ; 
hence its real orbit, during this time, is along the curved 
line a c. 



12. Position of the Solar System in Space. — 
The sun, with all the bodies which move around 
it, is in that portion of the heavens called the 
Milky Way. The sun is an insignificant star 
among the millions of other stars the telescope 
has revealed to us. 

It was formerly believed that the sun was stationary, for 
it was not then known that the positions of the fixed stars 
were undergoing slight variations as regards the earth. 
It is now generally conceded that the sun, with all the 
planets, is moving through space with tremendous veloc- 
ity, the direction at present being toward the constella- 
tion Hercules. The astronomer Maedler, however, believes 
that the grand centre around which the solar system is 
moving is Alcyone, the brightest star in the constellation 
of the Pleiades. The estimated velocity of the sun in its 
immense orbit is 1,382,000,000 miles per year. As the earth 
is carried along with the sun in its orbit, it is continually 
entering new realms of space. 

13. The Earth. — The shape of the earth is that 
of a round ball or sphere slightly flattened at two 
opposite sides. Such a body is termed a spheroid. 
There are two kinds of spheroids — oblate and pro- 
late; the former has the shape of an orange, the 
latter that of a lemon. 



MATHEMATICAL GEOGRAPHY. 



13 



The straight line that runs through the centre 
of a sphere or spheroid and terminates at the cir- 
cumference is called the diameter. If the sphere 
rotates — that is, moves around like a top — the 





Fig, 4. Oblate Spheroid, Pig. 5, Prolate Spheroid. 

diameter on which it turns is called its axis. In 
the oblate spheroid the axis is the shorter diam- 
eter ; in the prolate spheroid the axis is the longer 
diameter. 




Fig. 6. Curvature of the Earth's Surface. 

The shape of our earth is that of an oblate 
spheroid. The polar diameter is 26.47 miles 
shorter than the equatorial diameter. 

14. Proofs of the Rotundity of the Earth.— 



The earth is so large a sphere that its surface 
everywhere appears flat. The following simple 
considerations will prove, however, that its form 
is nearly spherical : 

(1.) Appearance of Approaching Objects, — If 
the earth were flat, as soon as an object appeared 
on the horizon we would see the upper and lower 
parts at the same time ; but if it were curved, the 
top parts would first be seen. Now, when a ship 
is coming into port we see first the topmasts, then 
the sails, and finally the hull ; hence the earth 
must be curved ; and, since the appearance is the 
same no matter from what direction the ship is 
approaching, we infer that the earth is evenly 
curved, or spherical. 

(2.) Circular Shape of the Horizon. — The hori- 
zon — or, as the word means, the boundary — is the 
line which limits our view when nothing inter- 
venes. The fact that this is always a circle fur- 
nishes another proof that the earth is spherical. 

The horizon would still be a circle if the earth were 
perfectly flat, for we would still see equally far in all di- 
rections ; but it would not everywhere be so, since to an 
observer near the edges some other shape would appear. 
It is on account of the spherical form of the earth that our 
field of view on a plain is so soon limited by the apparent 
meeting of the earth and sky. As we can see only in 
straight lines, objects continue visible until they reach 
such a distance as to sink below the horizon, so that a 
straight line from the eye will pass above them, meeting 
the sky far beyond, on which, as a background, the objects 
on the horizon are projected. 

(3.) Shape of the Earth's Shadow. — We can 
obtain correct ideas of the shape of a body by 
the shape of the shadow it casts. Now, the 
shadow which the earth casts on the moon dur- 
ing an eclipse of the moon is always circular, 
and as only spherical bodies cast circular shad- 
ows in all positions, we infer that the earth is 
spherical. 

(4.) Measurement. — The shape of the earth has 
been accurately ascertained by calculations based 
on the measurement of an arc of a meridian. We 
therefore not only know that the earth is oblately 
spheroidal, but also approximately the amount of 
its oblateness. 

(5.) The Shape of the Great Circle of Illumi- 
nation, or the line separating the portions of the 
earth's surface lighted by the sun's rays from 
those in the shadow, is another evidence cf the 
rotundity of the earth. 

15. The Dimensions of the Earth.— The equa- 
torial diameter of the earth, or the distance 
through at the equator, is, approximately, 7926 



14 



PHYSICAL GEOGRAPHY. 



miles ; its polar diameter, or the length of its 
axis, is 7899 miles. The circumference is 24,899 
miles. The entire surface is equal to nearly 
197,000,000 square miles. 

The specific gravity of the earth is about 5§ ; that is, the 
average weight of all its matter is five and two-third 
times heavier than an equal volume of water. 

16. Imaginary Circles. — In order to locate 
places on the earth, as well as to represent por- 
tions of its surface on maps, we imagine the earth 
to be encircled by a number of curved lines 
called great and small circles. 

A great circle is one which would be formed 
on the earth's surface by a plane passing through 
the earth's centre, hence dividing it into two 
equal parts. All great circles, therefore, divide 
the earth into hemispheres. 

The formation of a great circle on a sphere by cutting 
it into two equal parts is shown in Fig. 7. 



lik 



Fig. 7. Great Circle, 

The shortest distance between any two places on the 
earth is along the arc of a great circle. 

All planes passing through the earth's centre form ap- 
proximately great circles on its surface. 

A small circle is one formed by a plane which 
does not cut the earth into two equal parts. 

The formation of a small circle by cutting a sphere into 
unequal parts is shown in Fig. 8. 



■M 



Fig, 8. Small Circle, 

The great circles employed most frequently in 
geography are the equator and the meridian 
circles. The small circles are the parallels. 



If we divide the circumference of any circle, whether 
great or small, into three hundred and sixty equal parts, 
each part is called a degree. The oue-sixtieth part of a 
degree is a minute; the one-sixtieth part of a minute is a 
second. These divisions are represented as follows : 34°, 
12', 38'' ; which reads, thirty-four degrees twelve minutes 
and thirty-eight seconds. 

The Equator is that great circle of the earth 
which is equidistant from the poles. 

Meridian Circles are great circles of the earth 
which pass through both poles. 

The Meridian of any given place is that half 
of the meridian circle which passes through that 
place and both poles. A meridian of any place 
reaches from that place to both poles, and there- 
fore is equal to one-half of a great circle, and, 
with the meridian directly opposite to it, forms 
a great circle called a meridian circle. There 
are as many meridian circles as there are places 
on the equator or on any parallel. 

In large cities the meridian is generally assumed to pass 
through the principal observatory. 




Fig, 9. Meridians and Parallels, 

Parallels are small circles which pass around 
the earth parallel to the equator. 

The meridians extend due north and south, and are 
everywhere of the same length ; the parallels extend due 
east and west, and decrease in length as they approach the 
poles. 

The Tropics are parallels which lie 23° 27' 
north and south of the equator: the northern 
tropic is called the Tropic of Cancer, the south- 
ern tropic is called the Tropic of Capricorn. 

The Polar Circles are parallels which lie 23° 
27' from each pole. The circle in the Northern 
Hemisphere is called the Arctic Circle; that in 
the Southern Hemisphere, the Antarctic Circle. 

17. Latitude is distance north or south from 
the equator toward the poles, measured along 
the meridians. It is reckoned in degrees. 

The meridian circles are divided into nearly 
equal parts by the parallels, and it is the number 
of these parts that occur on the meridian of any 
place between it and the equator which deter- 



MATHEMATICAL GEOGRAPHY. 



15 



mines the value of its latitude. If we conceive 
eighty-nine equidistant parallels drawn between 
the equator and either pole, the) r will divide all 
the meridians into ninety nearly equal parts ; the 
value of each of these parts will be one degree 
of latitude. Therefore, if the parallel running 
through a place is distant from the equator forty- 
five of these parts, its latitude is 45°. If more 
than eighty-nine parallels be drawn, the value 
of each part will be less than one degree. 

Places north of the equator are in north lati- 
tude ; those south of it are in south latitude. 

Since the distance from the equator to the poles 
is one-fourth of an entire circle, and there are 
only 360° in any circle, 90° is the greatest value 
of latitude a place can have. Latitude 90° N. 
therefore corresponds to the north pole. 

To recapitulate : Latitude is measured on the 
meridians by the parallels. 

18. Longitude is distance east or west of any 
given meridian. 

Places on the equator have their longitude measured 
along it ; everywhere else longitude is measured along the 
parallels. 

The meridian from which longitude is reckoned 
is called the Prime Meridian. Most nations take 
the meridians of their own capitals for their prime 
meridian. The English reckon from the me- 
ridian which runs through the observatory at 
Greenwich ; the French from Paris. In the 
United States we reckon from Washington. 

Any prime meridian circle divides all the par- 
allels into two equal parts. A place situated east 
of the prime meridian is in east longitude ; west 
of it is in west longitude. 

Since there are only 180° in half a circle, the greatest 
value the longitude can have is 180° ; for a place 181° east 
of any meridian would not fall within the eastern half of 
the parallel on which it is situated, but in the western 
half; and its distance, computed from the prime meridian, 
would be 179° west. 

It is the meridians that divide the parallels 
into degrees ; therefore longitude is measured on 
the parallels by the meridians. 

19. Value of Degrees of Latitude and Longi- 
tude. — As latitude is distance measured on the 
arc of a meridian, the value of one degree must 
be the -g^-p-th part of the circumference along that 
meridian, since there are only 360° in all. This 
makes the value of a single degree approximately 
equal to 69£ miles. Near the poles the flattening 
of the earth causes the value of a degree slightly 
to exceed that of one near the equator. 



The value of a degree of longitude is subject 
to great variation. It is equal to the -youth p ar t 
of the earth's circumference, provided the place 
be situated on the equator; otherwise, it is the 
3^-jth part of the parallel passing through the 
place that is taken ; and as the parallels decrease 
in size as we approach the poles, the value of a 
degree of longitude must likewise decrease as the 
latitude increases, until at either pole the longi- 
tude becomes equal to zero. 

The value of a single degree of longitude on the equator, 
or at lat. 0°, is equal to aboift 69J miles. 
At latitude 45° it is equal to about 49 miles. 
60° " " 35 " 

" 80° " " 12 " 

90° " " " 

Geographical Mile.— The jrirriFth of the equatorial 
circumference, or the one-sixtieth of a degree of longitude 
at the equator, is called a nautical or geographical mile. 
The statute mile contains 1760 yards ; the geographical or 
nautical mile, 2028 yards. The nautical mile is sometimes 
called a knot. 

20. Map Projections. — The term projection as 
applied to map-drawing means the various methods 
adopted for representing portions of the earth's 
surface on the plane of a sheet of paper. 

The projections in most common use are Merca- 
tor's, the orthographic, the stereographic, and the 
conical projections. Of these the stereographic is 
best adapted to ordinary geographical maps, and 
Mercator's to physical maps. All projections 
must be regarded as but approximations. 

1. The Orthographic Projection is that by which the 
earth's surface is represented as it would appear to an 
observer viewing it from a great distance. 

2. The Stereographic Projection is that by which the 
earth's surface is represented as it would appear to an 
observer whose eye is directly on the surface, if he looked 
through the earth as through a globe of clear glass, and 
drew the details of the surface as they appeared projected 
on a transparent sheet of paper stretched in front of his 
eye across the middle of the earth. There may be an 
almost infinite number of such projections, according to 
the position of the observer. The two stereographic pro- 
jections in most common use are the Equatorial and the 
Polar. 

Mercator's Projection represents the earth on 
a map in which all the parallels and meridians 
are straight lines. 

Mercator's charts are drawn by conceiving the 
earth to have the shape of a cylinder instead of 
that of a sphere, and to be unrolled from this 
cylinder so as to form a flat surface. The me- 
ridians, instead of meeting in points at the north 
and south poles, are drawn parallel to each other. 
This makes them as far apart in the polar regions 



16 



PHYSICAL GEOGEAPHY. 



as at the equator, and consequently any portion 
of the earth's surface represented on such a chart, 
if situated toward the poles, will be dispropor- 


they approach the poles. The dimensions of the 
land or water, however, are greatly exaggerated 
in these regions. The immediate polar regions 
are never represented on such charts, the poles 




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In an Equatorial Projection of the entire earth 
the equator passes through the middle of each 
hemisphere, and a meridian circle forms the 
borders. 

In a Polar Projection of the entire earth the 




Fig. 11. The Earth on an Eqnatorial Projection. 



poles occupy the centres of each hemisphere, and 
the equator forms the borders. 
In a Conical Projection the earth's surface is 



represented as if drawn on the frustum of a cone 
and afterward unrolled. This projection is suit- 
able where only portions of the earth's surface, 




Fig. 12. The Earth on a Polar Projection, 



and not hemispheres, are to be represented. The 
cone is supposed to be placed so as to touch the 
earth at the central parallel of the country to be 
represented. 



In maps as ordinarily constructed it is not true that the 
upper part is north, the lower part south, the right hand 
east, and the left hand west, except in those on Merca- 
tor's projection. In all maps due north and south lie along 
the meridians, and due east and west along the parallels, since 






MATHEMATICAL GEOGRAPHY. 



17 




Fig. 13. The Conical Projection, 

in most maps both parallels and meridians are curved lines. 
Therefore, in most maps due north and south and due east 
and west will lie along the meridians and parallels, and 
not directly toward the top and bottom, or the right- and 
left-hand side. 

21. The Hemispheres. — The equator divides the 
earth into a Northern and a Southern Hemisphere. 

The meridian of long. 20° W. from Greenwich 
is generally taken as the dividing-line between 
the Eastern and Western Hemispheres. 

22. The Movements of the Earth ; Rotation. — 
The earth turns around from west to east on its 
diameter or axis. This motion is called its ro- 
tation. 

That the earth rotates from west to east the following 
consideration will show : To a person in a steam-car mov- 
ing rapidly in any direction, the fences and other objects 
along the road will appear to be moving in the opposite 
direction : their motion is of course apparent, and is caused 
by the real motion of the car. Now, the motion of the 
sun and the other heavenly bodies, by which they appear 
to rise in the east and set in the west, is apparent, and is 
caused by the real motion of the earth on its axis; this 
motion must therefore be from west to east. The sun, the 
planets, and their satellites, so far as is known, also turn 
on their axes from west to east. 

The earth makes one complete rotation in about 
every twenty-four hours — accurately, 23 hours 56 
minutes 4.09 seconds. The velocity of its rota- 
tion is such that any point on the equator will 
travel about 1042 miles every hour. The veloci- 
ty of course diminishes at points distant from the 
equator, until at the poles it becomes nothing. 

23. Change of Day and Night. — The earth re- 
ceives its light and heat from the sun, and, being 
an opaque sphere, only one-half of its surface can 
be lighted at one time. The other half is in dark- 
ness, since it is turned from the sun toward por- 
tions of space where it only receives the dim light 
of the fixed stars. The boundary-line between the 
light and dark parts forms approximately a great 
circle called the Great Circle of Illumination. Had 

3 



the earth no motion either on its axis or in its 
orbit, that part of its surface turned toward the 
sun would have perpetual day, and the other part 
perpetual night ; but by rotation different portions 
of the surface are turned successively toward and 
away from the sun, and thus is occasioned the 
change of day and night. 

24. The Revolution of the Earth.— The earth has 
also a motion around the sun, called its revolution. 

The revolution of the earth is from west to east; 
this is also true of all the planets and asteroids, 
and of all their satellites, except those of Uranus, 
and probably of Neptune. 

The phrases "rotation of the earth on its axis" and 
"revolution in its orbit" are often used in reference to 
the earth's motion ; but the simple words " rotation " and 
" revolution " are sufficient, since the first refers only to 
the motion on its axis, and the second only to the motion 
in its orbit. 

The earth makes a complete revolution in 365 
days 6 hours 9 minutes 9.6 seconds. This time 
forms what is called a sidereal year. The tropical 
year, or the time from one March equinox to the 
next, is somewhat shorter, or 365 days 5 hours 48 
minutes 49.7 seconds. The latter value is the one 
generally given for the length of the year. It is 
nearly 365 \ days. 

It will be found that the sum of the days in all the 
months of an ordinary year is only equal to 365, while the 
true length is approximately one-quarter of a day greater. 
This deficiency, which in every four years amounts to an 
entire day, is met by adding one day to February in every 
fourth or leap year. The exact time of one revolution, 
however, is some 11 minutes less than 6 hours. These 
eleven extra minutes are taken from the future, and are 
paid by omitting leap year every hundredth year, except 
that every 400 years leap year is counted. In other words, 
1900 will not be a leap year, since it is not divisible by 400, 
but the year 2000 will be a leap year. 

The length of the orbit of the earth is about 
577,000,000 miles. Its shape is that of an el- 
lipse which differs but little from a circle. The 
sun is placed at one focus of the ellipse, and, as 
this is not in the centre of the orbit, the earth 
must be nearer the sun at some parts of its revo- 
lution than at others. 

When the earth is in that part of its orbit which is near- 
est to the sun, it is said to be at its perihelion; when in 
that part farthest from the sun, at its aphelion. The peri- 
helion distance is about 90,259,000 miles ; the aphelion dis- 
tance, 93,750,000 miles. The earth reaches its perihelion 
about January 1st. 

The earth does not move with the same rapidity through 
all parts of its orbit, but travels more rapidly in perihelion 
than in aphelion. Its mean velocity is about 19 miles a 
second, which is nearly sixty times faster than the speed 
of a cannon-ball. 



18 



PHYSICAL GEOGRAPHY. 



25. Laplace's Nebular Hypothesis. — The uniformity 
in the direction of rotation and revolution of the planets 
has led to a very plausible supposition as to the origin of 
the solar system, by the celebrated French astronomer La- 
place. This supposition, known as Laplace's nebular hy- 
pothesis, assumes that, originally, all the materials of which 
the solar system is composed were scattered throughout 
space in the form of very tenuous or nebulous matter. It 
being granted that this matter began to accumulate around 
a centre, and that a motion of rotation was thereby ac- 
quired, it can be shown, on strict mechanical principles, 
that a system resembling the solar system might be evolved. 

As the mass contracted on cooling, the rapidity of its 
rotation increased. The equatorial portions bulged out 
through the centrifugal force, until ring-like portions 
separated, and, collecting in spherical masses, formed the 
planets. The planets in a similar manner detached their 
satellites. At the time of the separation of Neptune the 
nebulous sun must have extended beyond the orbit of this 
planet. The temperature requisite for so great an expan- 
sion must have been enormous. 

Although a mere hypothesis, there are many facts which 
tend to sustain it, and it is now generally accepted. 

26. The Plane of the Earth's Orbit is a per- 
fectly fiat surface so placed as to touch the earth's 
orbit at every point. It may be regarded as an 
imaginary plane of enormous extent on which the 
earth moves in its journey around the sun. 

27. Causes of the Change of Seasons. — The 
change of the earth's seasons is caused by the 
revolution of the earth, together with the fol- 
lowing circumstances : 




Fig. 14, Inclination of Axis to Orbit and Ecliptic. 



(1.) The inclination of the earth's axis to the 
plane of its orbit. The inclination is equal to 
66° 33'. 

The ecliptic is the name given to a great circle whose 
plane coincides with the plane of the earth's orbit. Since 
the earth's axis is 90° distant from the equator, the plane 
of the ecliptic must be inclined to the plane of the equator 
90° minus 66° 33', or 23° 27'. 

The mere revolution of the earth would be unable to 
produce a change of seasons, unless the earth's axis were 
inclined to the plane of its orbit. If, for example, the 
axis of the earth stood perpendicularly on the plane of its 
orbit, the sun's rays would so illumine the earth that the 
great circle of illumination would always be bounded by 
some meridian circle. The days and nights would then 
be of equal length, and the distribution of heat the same 
throughout the year. Under these circumstances there 
could be no change of seasons, since the sun's rays would 



always fall perpendicularly on the same part of the earth : 
on the equator. 

(2.) The Constant Parallelism of the Earth's 
Axis. — During the earth's revolution its axis 
always points nearly to the same place in the 
heavens, viz. to the north star. It is therefore 
always approximately parallel to any former 
position. 

Unless the axis were constantly parallel to any former 
position, the present change of seasons would not occur. 

On account of the spherical form of the earth, 
only a small part of its surface can receive the 
vertical rays of the sun at the same time. This 
part can be regarded as nearly a point ; and since 
only one-half of the earth is lighted at any one 
time, the great circle of illumination must extend 
90° in all directions from the point which receives 
the vertical rays. By rotation all portions of 
the surface situated anywhere within the tropics 
in the same latitude, at some time or another 
during the day, are turned so as to receive the 
vertical rays of the sun, and consequently, the 
portion so illumined has the form of a ring or 
zone. Other things being equal, this zone con- 
tains the hottest portions of the surface, the heat 
gradually diminishing as we pass toward either 
pole. 

On account of the inclination of its axis, the 
earth receives the vertical rays of the sun on new 
portions of its surface every day during its revo- 
lution ; and it is because different portions of the 
surface are constantly being turned toward the stm 
that the change of seasons is to be attributed. 

As the earth changes its position in its orbit, the 
sun's rays fall vertically on different parts of the 
surface, so that during the year one part or an- 
other of the surface within 23° 27' on either side 
of the equator receives the vertical rays. 

The astronomical year begins on the 20th 
of March, and we shall therefore first consider 
the position of the earth in its orbit at that 
time. 

An inspection of Fig. 15 will show that at this 
time the earth is so turned toward the sun that 
the vertical rays fall exactly on the equator. The 
great circle of illumination, therefore, reaches to 
the poles, and the days and nights are of an equal 
length all over the earth. This time is called the 
March equinox. Spring then begins in the North- 
ern Hemisphere, and autumn in the Southern. 
This is shown more clearly in Fig. 16, which 
represents the relative positions of the illumined 
and non-illumined portions at that time. 



MATHEMATICAL GEOGRAPHY. 




Pig. 15. The Orbit of the Earth, showing the Change of Seasons. 



As the earth proceeds in its orbit, the inclina- 
tion of the axis causes it to turn the Northern 
Hemisphere more and more toward the sun. The 
vertical rays, therefore, fall on portions farther 
and farther north until, on the 21st of June, the 




Pig. 16. The Earth at an Equinox, 

vertical rays reach their farthest northern limit, 
and fall directly on the Tropic of Cancer, 23° 27' 
N., when the sun is said to be at its summer sol- 
stice. 

Since the portions receiving the vertical rays 
of the sun are now on the Tropic of Cancer, 



the light and heat must extend in the Northern 
Hemisphere to 23° 27' beyond the north pole, or 
to the Arctic Circle ; while in the Southern Hemi- 
sphere they must fall short of the south pole by 
the same number of degrees, or reach to the Ant- 




Fig. 17. The Earth at the Summer Solstice. 

arctic Circle. The Northern Hemisphere then be- 
gins its summer, and the Southern its winter. 

The relative positions of the illumined and 
non-illumined portions of the earth at the sum- 
mer solstice are more clearly shown in Fig. 17. 
Here, as is shown, the creat circle of illumination 



20 



PHYSICAL GE.OGRAPHY. 



extends in the Northern Hemisphere as far over 
the pole as the Arctic Circle. 

After the 21st of June the Northern Hemi- 
sphere is turned less toward the sun, and the 
vertical rays continually approach the equator, 
all the movements of the preceding season being 
reversed, until on the SSd of September, the time 
of the September equinox, the equator again receives 
the vertical rays, the great circle of illumination 
again coinciding with the meridian circles. The 
earth has now moved from one equinox to an- 
other, and has traversed one-half of its orbit. 
The Southern Hemisphere then begins its spring, 
the Northern its autumn. 

From the 22d of September until the 20th of 
March, while the earth moves through the other 
half of its orbit, the same phenomena occur in 
the Southern Hemisphere that have already been 
noticed in the Northern. Immediately after the 
22d of September the inclination of the axis 
causes the earth to be so turned toward the sun 
that its rays begin to fall south of the equator ; 
and, as the earth proceeds in its orbit, the South- 
ern Hemisphere is turned more and more toward 
the sun, and the vertical rays fall farther and 
farther toward the pole. This continues until 
the 21st of December, when the rays fall vertically 
on the Tropic of Capricorn, and the December sol- 
stice is reached. The great circle of illumination 
now extends beyond the south pole as far as the 
Antarctic Circle, but falls short of the north pole 
23° 27', reaching only the Arctic Circle. (Stam- 
mer then commences in the Southern Hemisphere, 
and winter in the Northern. 

After the 21st of December the Southern 
Hemisphere is turned less and less toward the 




Fig. 18. Mathematical Climatic Zones. 

sun, and the part receiving the vertical rays 
approaches the equator, until on the 20th of 



March the equator again receives the vertical 
rays, and, with the March equinox, spring com- 
mences in tlie Northern Hemisphere, and with 
it a new astronomical year. 

The equinoxes and solstices as a rule occur on the dates 
named. Occasionally they occur immediately before or 
after said dates. 

28. Mathematical Zones. — The Torrid Zone. — 
That belt of the earth's surface which lies be- 
tween the tropics is called the Torrid Zone. 
During one time or another throughout the 
year every part of its surface receives the ver- 
tical rays of the sun. 

The Temperate Zones are included between the 
tropics and the polar circles. The northern zone 
is called the North Temperate Zone, and the south- 
ern zone, the South Temperate Zone. 

The Polar Zones are included between the 
polar circles and the poles. The northern zone 
is called the North Frigid Zone, and the southern 
zone, the South Frigid Zone. 

These zones, which are separated by the parallels of lati- 
tude, are generally termed the astronomical or mathematical 
zones to distinguish them from others called physical zones, 
which are bounded by the lines of mean annual temper- 
ature. 

It will be noticed that the distance of the tropics from 
the equator and of the polar circles from the poles is 23° 
27', or the value of the inclination of the plane of the 
ecliptic to the plane of the equator. 

29. Length of Bay and Night. — Whenever 
more than half of either the Northern or South- 
ern Hemisphere is illumined, the great circle of 
illumination will divide the parallels unequally, 
and the length of the daylight in that hemisphere 
•will exceed that of the night in proportion as the 
length of the illumined part, measured along any 
of the parallels, exceeds that of the dark part. 

The length of daylight or darkness may exceed 
that of one complete rotation of the earth. The 
great circle of illumination may at times pass 
over the poles as far beyond them as 23° 27'; 
and places situated within this limit may remain 
during many rotations exposed to the rays of the 
sun. 

A little consideration will show that the longest day 
must occur at the poles, since the poles must continue 
to receive the sun's rays from the time they are first illu- 
mined at one equinox until the sun passes through a sol- 
stice and returns to the other equinox. Nowhere, outside 
the polar circles, will the length of daylight exceed one 
entire rotation of the earth. 

The length of the longest day at the equator, latitude 
0°, is 12 hours. 

Of the longest day at the poles, latitude 90°, is six 
months. 



MATHEMATICAL GEOGRAPHY. 



21 



SYLLABUS. 



There are three kinds of geography — Mathematical, Po- 
litical, and Physical. 

Physical Geography treats of Land, Water, Air, Plants, 
Animals, and Minerals. 

Geography deals mainly with the earth as it is ; geology 
mainly with the earth as it was. 

The earth continues its motion around the sun in conse- 
quence of its inertia. 

The distant stars are balls of fire like our sun, and prob- 
ably have worlds resembling ours revolving around them. 

The sun and the bodies that revolve around it consti- 
tute the solar system. 

The sun is about 1,300,000 times larger than the earth. 

The sun is a body heated to luminosity, and gives out or 
emits light and heat like any other highly-heated body. 

The shape of the earth is that of an oblate spheroid 
whose equatorial diameter is about 26 miles longer than 
its polar. That the earth is round and not flat is proved 
— 1st, by the appearance of approaching or receding ob- 
jects ; 2d, by the circular shape of the horizon ; 3d, by the 
circular shape of the earth's shadow ; 4th, by actual meas- 
urement ; and 5th, by the shape of the great circle of 
illumination. 

The earth's diameter is nearly 8000 miles, its circumfer- 
ence not quite 25,000 miles, and its area about 197,000,000 
square miles. 

The imaginary circles used in geography are the Equa- 
tor, the Meridian Circles, and the Parallels. 

Latitude is measured on the meridians by the parallels. 



The greatest number of degrees of latitude a place can 
have is 90° ; the greatest of longitude, 180°. The latitude 
at the equator is 0° N. or S. The longitude at the poles or 
on the prime meridian is 0° E. or W. 

Longitude is measured on the equator*oron the parallels, 
by the meridians. 

Maps are drawn on different projections : the Equatorial, 
the Polar, and Mercator's projections are in most general 
use. A Mercator's projection causes places near the poles 
to appear larger than they really are. 

On all maps due north and south lies along the merid- 
ians; due east and west, along the parallels : when these 
are curved lines, the top and bottom of the map will not 
always represent north and south, nor the right and left 
hand east and west. 

The inclination of the earth's axis to the plane of its 
orbit, and the constant parallelism of the axis with any 
former position, together with the revolution around the 
sun, cause the change of seasons. 

The astronomical year begins March 20th. 

On the 20th of March and on the 22d of September the 
days and nights are of equal length all over the earth. 
From the 20th of March the days increase in length in the 
Northern Hemisphere until the 21st of June, when they 
attain their greatest length ; they then decrease until the 
22d of September, when they again become equal. 

The Torrid Zone is the hottest part of the earth, because, 
during one time or another throughout the year, every part 
of its surface receives the vertical rays of the sun. 



REVIEW QUESTIONS. 



The Solar System. 

How does the principle of inertia apply to the earth's 
motion around the sun? 

What do you understand by the solar system? 

Describe the earth's position in the solar system. Which 
of the planets are between the earth and the sun? Which 
are beyond the orbit of the earth? 

How does the size of the sun compare with that of the 
earth ? 

Are any of the distant stars larger than our sun ? 

What is a satellite ? Which of the planets have satellites ? 

Explain the cause of the circular shape of the earth's 
orbit. 

In what part of space is the solar system ? 

Has our sun any motion through space? 

Enumerate the proofs of the rotundity of the earth. 

State accurately the length of the equatorial diameter 
of the earth ; of its polar diameter ; of its circumference. 
What is its area ? 

How many times heavier is the earth than an equally 
large globe of water? 

Imaginary Circles. 

Define great and small circles. Name the circles most 
commonly used in geography. 

What do you understand by latitude? How is latitude 
reckoned ? Of what use is latitude in geography ? Why 



can the value of the latitude never exceed 90° ? Of what 
use are meridians and parallels in measuring latitude? 

What do you understand by longitude? How is longi- 
tude reckoned? Of what use is longitude in geography? 
Why can its value never exceed 180° ? Of what use are 
meridians and parallels in measuring longitude? 

Where is the value of a degree of latitude the greatest? 
Of a degree of longitude ? Why ? 

What effect has a Mercator's chart on the appearance of 
bodies of land or water in high northern or southern lati- 
tudes? 

What is an equatorial projection? A polar projection? 
A conical projection? What is the position of the poles in 
an equatorial projection? In a polar projection ? 

Movements of the Earth. 

Prove that the earth turns on its axis from west to east. 

Explain the cause of the change of day and night. 

Define a sidereal year ; a tropical year. Which value is 
generally taken for the length of the civil year? 

Describe Laplace's nebular hypothesis. 

Enumerate the causes which produce the change of 
seasons. 

On what days of the year will the sun's rays fall verti- 
cally on the equator ? On what days will its rays fall ver- 
tically on the Tropic of Cancer? On the Tropic of Capri- 
corn? 



Part II. 



THE LAND. 



«XKo 




Although water occupies much the larger portion of the earth's surface, yet, when compared with 
the entire volume of the globe, its quantity is comparatively insignificant ; for the mean depth of the 
ocean probably does not exceed two and one-third miles, and underneath this lies the solid crust, 
with its heated interior. 

The crust and heated interior are composed of a variety of simple and compound substances. Simple 
or elementary substances are those which have never been separated into components. Compound 
substances are those which are composed of two or more simple or elementary substances combined 
under the influence of the chemical force. 



Section I. 



THE INSIDE OF THE EARTH. 



CHAPTER I. 

The Heated Interior. 

30. The Proofs of the Earth's Original Fluidity 
or fused condition through heat are — 

(1.) Its Spherical Shape, which is the shape 
the earth would have taken had it been placed 
in space when in a melted condition. This is 
the shape of nearly all the heavenly bodies. 

22 



(2.) The fact that the rocks which were first 
formed give evidence by their appearance of 
having been greatly heated. These rocks are 
generally highly crystalline. 

(3.) The general climate of the earth during 
the geological past was much warmer than at 
present. 

Very little of the internal heat now reaches the surface. 
According to Poisson, all that escapes would raise the mean 
annual temperature only ^th of a degree Fahr. 



VOLCANOES. 



23 



31. Laplace's Nebular Hypothesis agrees very well 
with the idea of a former igneous fluidity, since, at the 
time of its separation from the nebulous sun, the earth 
must have had a temperature sufficient not only to fuse, 
but even to volatilize, most of its constituents. 

32. Proofs of a Present Heated Interior. — The 

following considerations show that the inside of 
the earth is still highly heated : 

(1.) The deeper we penetrate the crust, the 
higher the temperature becomes. Moreover, the 
rate of increase, though varying in different lo- 
calities with the character of the materials of the 
crust, is nearly uniform over all parts of the sur- 
face, the average value of the increase being 1° 
Fahr. for every 55 feet of descent. 

This would seem to indicate that the entire 
inside of the earth is heated, and that the heat 
increases as we go toward the centre. 

We cannot, however, estimate the thickness of the crust 
from this fact — 

1. Because we have never penetrated the crust more 
than a few thousand feet below the level of the sea, and 
therefore we do not know that this rate of increase of 
temperature continues the same : 

2. Even if it did continue uniform, since the melting- 
point of solids increases with the pressure, we do not 
know what allowance should be made for this increase. 

(2.) In all latitudes prodigious quantities of 
melted rock escape from the interior through 
the craters of volcanoes. The interior, there- 
fore, must be hot enough to melt rock. 

33. Condition of the Interior. — We do not 
know the condition of the material which fills 
the interior of the earth. It might be supposed, 
since rock escapes from the craters of volca- 
noes in a fluid or molten condition, that the in- 
terior is filled with molten matter ; but this is 
not necessarily so, since the enormous pressure 
to which the interior is subjected would prob- 
ably be sufficient to compress it into a viscous 
or pasty mass, or, possibly, even to render it solid. 
The lava which issues from the crater of a vol- 
cano is necessarily more mobile than the interior 
of the earth ; for, coming, as it does, from great 
depths, it must grow more and more liquid as it 
approaches the surface and is thus relieved of its 
pressure. Indeed, the most viscous rock conceiv- 
able, if highly heated when ejected from pro- 
found depths, would become comparatively fluid 
on reaching the surface. 

34. Views Concerning the Condition of the 
Interior. — Considerable difference of opinion ex- 
ists as to the exact condition of the interior of 
the earth. The following opinions may be men- 
tioned : 



(1.) That the earth has a solid centre and 
crust, with a heated or pasty layer between. 

(2.) That the crust is solid, but the interior 
highly heated, so as to be in a fused or pasty 
condition. 

(3.) That the earth is solid throughout, but 
highly heated in the interior. 

Of the above views, the second is perhaps the 
most tenable, and will be adopted as serving in 
the simplest manner to explain the phenomena 
of the earth arising from the presence of a highly 
heated interior. Admitting the crust to be suf- 
ficiently thin, and in such a condition as to per- 
mit of but a small degree of warping, then all 
the phenomena can be satisfactorily explained. 

35. Thickness of the Crust. — We cannot as- 
sign a definite limit to the thickness of the crust, 
since the portions that are solid from having 
cooled, most probably pass insensibly into those 
that are nearly solid from the combined influence 
of loss of heat and increasing pressure. It seems 
probable that the portion solidified by cooling is 
thin, when compared with the whole bulk of the 
earth ; in other words, the heated interior lies 
comparatively near the surface. 

36. Effects of the Heated Interior. — As the 
crust loses its heat it shrinks or contracts, and, 
growing smaller, the materials of the interior are 
crowded into a smaller space, and an enormous 
force is thus exerted, both on the interior and on 
the crust itself, tending either to change the shape 
of the crust, to break it, or to force out some of 
the interior. The following phenomena are there- 
fore caused by the contraction of the crust : 

(1.) Volcanoes; 
(2.) Earthquakes ; 
(3.) Non-volcanic igneous eruptions ; 
(4.) Gradual elevations or subsidences of the 
crust. 



CHAPTER II. 

Volcanoes. 

37. Volcanoes. — One of the most striking proofs 
of the existence of a heated interior is the ejection 
of enormous quantities of melted rock through 
openings in the crust. 

A volcano is a mountain, or other elevation, 
through which the materials of the interior escape 
to the surface. The opening is called the crater, 
and may be either on the top or on the sides of 
the mountain. 



24 



PHYSICAL GEOGRAPHY. 




Fig, 19. An Eruption of Mount Vesuvius, 

38. Peculiarities of Craters. — The crater, as its name 
indicates, is cup-shaped. The rim, though generally entire, 
is sometimes broken by the force of the eruption, as in 
Mount Vesuvius, where the eruption in 79 A. D. — the first 
on record — blew off the northern half of the crater. The 
material thus detached, together with the showers of ashes 
and streams of lava, completely buried the cities of Her- 
culaneum and Pompeii, situated near its base. 

The crater is often of immense size. Mauna Loa, on the 
island of Hawaii, has two craters — one on the summit, and 
the other ou the mountain-side, about 4000 feet above the 
sea. The latter — Kilauea — is elliptical in shape, and about 
7i miles in circumference ; its area is nearly 4 square miles, 
and its depth, from 600 to 1000 feet. 

Volcanic mountains are of somewhat different 
shapes, but near the crater the conical form pre- 
dominates, and serves to distinguish these moun- 
tains as a class. The shape of the volcanic cone 
is caused by the ejected materials accumulating 
around the mouth of the crater in more or less 
concentric layers. 

39. The ejected materials are mainly as fol- 
lows : 

(1.) Melted Bock, or Lava. — Lava varies, not 
only with the nature of the materials from which 
it was formed, but also with the conditions under 
which it has cooled, and the quantity of air or 
vapor entangled in it. Though generally of a 
dark gray, it occurs of all colors ; and its texture 
varies from hard, compact rock to porous, spongy 
material that will float on water. 

When just emitted from the crater, ordinary lava flows 
about as fast as molten iron would on the same slope. On 
steep mountains, near the crater, the lava, when very 
hot, may flow faster than a horse can gallop ; but it soon 



cools, and becomes covered with a crust that greatly re- 
tards the rapidity of its flow, until its motion can only be 
determined by repeated observations. 

At Kilauea, jets of very liquid lava are sometimes 
thrown out, which, falling back into the crater, are drawn 
out by the wind into fine threads, thus producing what 
the natives call Pele's hair, after their mythical goddess. 

The volume of the ejected lava is often very great. Vol- 
canic islands are generally formed entirely by lava streams. 
Hawaii and Iceland were probably formed entirely of lava, 
emitted from numerous volcanic cones. 

(2.) Ashes or Cinders. — These consist of minute 
fragments of lava that are ejected violently from 
the crater ; at night they appear as showers of 
brilliant sparks. When they fall directly back 
on the mountain, they aid in rearing the cone. 
More frequently, they are carried by the wind to 
points far distant. The destructive effects of 
volcanic eruptions are caused mainly by heavy 
showers of ashes. The ashes, when exceedingly 
fine, form what is called volcanic dust. 

At the beginning of an erujrtion large frag- 
ments of rock are sometimes violently thrown 
out of the crater. 

(3.) Vapors, or Gases. — The vapor of water 
often escapes in great quantities from the crater, 
especially at the beginning of the eruption. On 
cooling, it condenses and forms dense clouds, from 
which torrents of rain fall. These clouds, lighted 
by the glowing fires beneath, appear to be actually 
burning, and thus give rise to the erroneous belief 
that a volcano is a burning mountain. To the 
condensation of this vapor is probably to be as- 
cribed the lightning which often plays around the 
summit of the volcano during an eruption. Be- 
sides the vapor of water, various gases escape, of 
which sulphurous acid is the most common. 

When a large quantity of rain mingles with the ashes, 
torrents of mud are formed, which move with frightful 
velocity down the slopes of the mountain, occasioning con- 
siderable damage. During the eruption of Galungung, in 
Java, more than one hundred villages were thus destroyed. 
The rock that is formed by the hardening of volcanic mud 
is called tufa. 

40. The Inclination of the Slopes of the vol- 
canic cones depends on the nature of the material 
of which they are formed. Where lava is the 
main ingredient, the cone is broad and flat The 
inclination of a lava cone ranges from 3° to 10°, 



Fig, 20, Lava Cone. Inclination from 3° to 10°. 

according to the liquidity of the lava. A very 
stiff lava will form a much steeper cone. 



VOLCANOES. 



25 



Ashes and cinders form steeper cones, whose 
inclinations range from 30° to 45°. 




Fig, 21. Ash Cone. Inclination from 30° to 45°. 

The sides of volcanic cones are often rent dur- 
ing the eruption, and the fissures filled with lava, 
which hardens and forms rocky ribs called dykes. 
Sometimes the central cone becomes choked, and 
secondary or parasitic cones are formed. 




Tig. 22. Volcanic Dykes and Parasitic Cones, 

41. The Cause of Volcanic Eruptions. — As the 

heated earth cools and the crust contracts, the ma- 
terials of the interior are crowded into a smaller 
space, and an enormous force is exerted, which 
causes portions of the interior to rise from profound 
depths and escape through openings in the crust. 
These openings form the craters of volcanoes. 

The principal agency, therefore, which brings 
up the heated material from great depths is the 
contraction of the crust on cooling. The melted 
rock thus brought into the volcano may escape — 

(1.) By the pressure of highly-heated gases or 
vapors, mainly that of water, which throws the 
lava explosively from the crater. 

(2.) By the pressure exerted by a column of 
liquid lava. Before the lava can run over the 
edge of the crater near the top of the mountain, 
the pressure caused by its weight becomes so great 
that the sides of the mountain are broken, and 
the lava escapes quietly from a lower opening. 

42. Other Explanations of Volcanic Action. — The 
above theory of volcanic action is not accepted by all sci- 
entists. Instead of an originally heated globe that has 
not yet completely cooled, it is asserted by some that heat 
is now being produced either by some chemical means, 
such as oxidation or hydration, or by a mechanical crush- 
ing of deep-seated strata. These explanations assume that 
the seat of the lava is not the entire interior of the earth, 
but that it is purely local, existing in comparatively shal- 



low basins or reservoirs not far from the surface. The 
peculiarities of distribution of volcanoes would appear to 
disprove the latter assumption. 

43. Volcanic Eruptions may be divided into 
two classes: explosive and non-explosive. 

Explosive eruptions are caused by the sudden 
formation of highly-heated vapors. 

In boiling water, drops are thrown from the 
surface by the bursting of bubbles of steam. 
This action is similar to that of explosive vol- 
canic eruptions. When the liquid is viscous, 
like tar, the escaping vapor accumulates in large 
bubbles, the bursting of which scatters the mate- 
rial in all directions. 

On account of the great viscidity of some lavas, the 
evolved gases accumulate until considerable force is ac- 
quired. At Kilauea, liquid jets are thrown upward to the 
height of 40 feet. With very viscid lavas, like those of 
Vesuvius, bubbles of enormous size are suddenly formed, 
which burst with almost incredible force. Cases are on 
record in which it is estimated the ashes were projected 
10,000 feet above the mouth of the crater. 

Non-explosive eruptions are caused by the 
pressure of a column of liquid lava. 

In non-explosive eruptions the lava escapes 
quietly through a fissure which opens in the 
mountain's side by the pressure exerted by the 
column of liquid lava in the crater. 

Since a column of lava 500 feet high exerts a pressure 
of about 625 pounds to the square inch, when the moun- 
tain is high the pressure against the sides of the crater 
may be sufficient to rend the solid rock. 

Vesuvius is an example of an explosive eruption ; Kila- 
uea and Etna, of non-explosive eruptions. 

Volcanic mountains whose eruptions are non- 
explosive are generally high; the lava can thus 
accumulate in the crater until it forces its way 
through fissures below. Volcanic mountains whose 
eruptions are explosive are generally low. 

Volcanoes are of common occurrence at the 
bottom of the ocean. These are called submarine 
volcanoes. During eruptions their cones some- 
times project above the water; but they gene- 
rally soon afterward disappear. 

44. Active and Extinct Volcanoes. — Volcanoes 
may be classified as active and extinct. 

Active Volcanoes are those which emit smoke, 
vapor, ashes, or lava from the crater. 

By an active volcano we do not mean one that is con- 
tinually in a state of eruption — ejecting ashes and lava — 
but one from which at least smoke or vapor is escaping. 
The crater may at any time become permanently choked, 
when the volcano becomes extinct. It may, however, open 
at any time, after extended intervals of rest, when the 
volcano again becomes active. 



Page 26. 




VOLCANOES. 



27 



45. The number of volcanoes is not accurately- 
known. The best authorities estimate it at about 
672, of which 270 are active. Of the latter, 175 
are on islands, and 95 are on the coasts of the con- 
tinents. 

46. Regions of Volcanoes. — The principal vol- 
canic regions of the earth are — * 

(1.) Along the Shores of the Pacific, where an 
immense chain of volcanoes, with but few breaks, 
encircles it in a huge "Sea of Fire." 

On the Eastern Borders, in the Andean range, 
are the volcanic series of Chili, Bolivia, and Ecua- 
dor ; those of Central America and Mexico ; in 
the United States are the series of the Sierra 
Nevada and Cascade ranges and of Alaska ; and 
finally, connecting the system with Asia, the vol- 
canic group of the Aleutian Islands. 

On the Western Borders volcanoes occur in the 
following districts : the Kamtchatkan Peninsula, 
with its submerged ranges of the Kurile Islands ; 
the Japan, the Loo Choo, and the Philippine 
Islands ; the Moluccas ; the Australasian Island 
Chain, terminating in New Zealand ; and finally, 
nearly in a line with these, the volcanoes of Ere- 
bus and Terror on the Antarctic continent. 

(2.) In the Islands of the Pacific. — Volcanic 
activity is not wanting over the bed of the Pa- 
cific. The Sandwich Islands, the Society Group, 
the Marquesas, Friendly Islands, New Hebrides, 
Ladrones, and many others, are volcanic. 

(3.) Scattered over the Seas that divide the 
Northern and Southern Continents, or in their 
vicinity, viz. : in the neighborhood of the Carib- 
bean Sea, in the Mediterranean and Pied Seas, 
and in the Pacific and Indian Oceans between 
Asia and Australia. 

In the neighborhood of the Caribbean Sea. — This 
region includes the two groups of the Antilles in 
the Caribbean Sea, and the Gallapagos Islands in 
the Pacific Ocean. 

In the neighborhood of the Mediterranean and 
Red Seas. — This region includes the volcanoes of 
the Mediterranean and its borders, those of" Italy, 
Sicily, the Grecian Archipelago, of Spain, Central 
France, and Germany, together with those near 
the Caspian and Red Seas. 

Between Asia and Australia. — This region in- 
cludes the Sunda Islands, Sumatra, Java, Sum- 
bawa, Flores, and Timor, which contain numerous 
craters. In Java there are nearly 50 volcanoes, 
28 of which are active, and there are nearly as 

* We follow mainly the classification of Dana. 



many in Sumatra. There are 1G9 volcanoes in 
the small islands near Borneo. 

(4.) In the Northern and Central Parts of the 
Atlantic Ocean. 

All the islands in the deep ocean which do not 
form a part of the continent are volcanic ; as, 
for example, the island of St. Helena, Ascension 
Island, the Cape Verdes, the Canaries, the Azores. 
and Iceland. The Cameroons Mountains, on the 
African coast near the Gulf of Guinea, together 
with some of the islands in the gulf, are volcanic. 

(5.) In the Western and Central Parts of the 
Indian Ocean. 

Volcanoes are found in Madagascar and in the 
adjacent islands. They also occur farther south, 
in the island of St. Paul and in Kerguelen Land, 
and in Kiliinandjaro, near the eastern coast of 
Africa. 

47. Submarine Volcanoes. — From the difficulty iu ob- 
serving them, submarine volcanoes are not so well known 
as the others. The following regions are well marked : 

In the Mediterranean Sea, near Sicily and Greece. 

Near the island of Santorin the submarine volcanic en- 
ergy is intense. It has been aptly described as a region 
"Where isles seem to spring up like fungi in a wood." 

In the Atlantic Ocean ; off the coast of Iceland ; near 
St. Michael, in the Azores ; and over a region in the nar- 
rowest part of the ocean between Guinea and Brazil. 

In the Pacific Ocean ; near the Aleutian Islands, 
where two large mountain-masses have risen from the 
water within recent time. Near the Japan Islands, where, 
about twenty-one centuries ago, according to native his- 
torians, Fusi Yama, the highest mountain in Japan, rose 
from the sea in a single night. 

In the Indian Ocean, the island of St. Paul, in the 
deep ocean between Africa and Australia, exhibits signs 
of submarine activity. 

48. Peculiarities of Distribution. — Nearly all 
volcanoes are found near the shores of continents 
or on islands. 

The only exceptions are found in the region 
south of the Caspian Sea, and in that of the 
Thian Shan Mountains. As volcanoes are but 
openings in the earth's crust which permit an es- 
cape of materials from the pasty interior, they 
will occur only where the crust is weakest. This 
will be on the borders of sinking oceans, in the 
lines of fracture formed by the gradual separa- 
tion of the ocean's bed from the coasts of the 
continent. The floor of the ocean in all latitudes 
is covered with a layer of quite cold water, so 
that the difference in the amount of the contrac- 
tion will in general be most marked on the bor- 
ders of the oceans or on the edges of the conti- 
nents. 

In most regions the volcanoes lie along lines 



28 



PHYSICAL GEOGRAPHY. 



more or less straight. Lines joining such a series 
may be considered as huge cracks in the crust, 
the volcanic phenomena occurring in their weak- 
est places. 

The frequent occurrence of volcanoes in moun- 
tainous districts is caused by the crust being 
broken and flexed, so as to admit of an easy 
passage for the molten rock. 

Where one system of fissures crosses another the 
crust becomes weak, the openings numerous, and the 
volcanic activity great. The two antipodal points 
of the Antilles and the Sunda Islands are excel- 
lent examples, and are the most active volcanic 
regions on the earth. 

Efforts have been made to show some connection be- 
tween certain states of the weather and periods of vol- 
canic activity ; but, so far, these have amounted to mere 
predictions of coming changes, based on observations of 
the direction of upper currents of air from the clouds 
of ashes or smoke ejected by the volcano. No law of 
periodicity of eruption has, as yet, been discovered. 

49. Other Volcanic Phenomena : 

Mud Volcanoes are small hillocks that emit 
streams of hot mud and water from their craters, 
but never molten rock. They are found in vol- 
canic regions. 

Solfataras are places where sulphur vapors es- 
cape and form incrustations. They occur in vol- 
canic regions. 

Geysers are sometimes ranked with volcanic phe- 
nomena. They are described under Hot Springs. 



oj«o 



CHAPTER III. 
Earthquakes. 

50. Earthquakes are shakings of the earth's 
crust, of degrees varying in intensity from 
scarcely perceptible tremors to violent agita- 
tions that overthrow buildings and open huge 
fissures in the ground. They may therefore be 
divided into two classes : 

(1.) A shaking movement without any perma- 
nent change in the surface ; 

(2.) A shaking movement accompanying an 
uplift or subsidence. 

An earthquake is sometimes called a seismic 
shock. 

51. Facts concerning Earthquakes. — A careful 
study of earthquakes appears to establish the fol- 
lowing facts : 

(1.) The place or origin of the shock is not 
deep-seated or far below the earth's surface, but 




Pig. 23. Fissures produced by the Charleston Earthquake of 1886. 

is near the surface, probably never deeper than 
thirty miles, and often much less. 

(2.) The area of disturbance depends not only 
on the energy of the shock, but also on the depth 
of its origin below the surface : the deeper the 
origin, the greater the area. 

(3.) The shape of the origin is generally that 
of a line, often many miles in length. 

(4.) The direction of the motion at the surface 
is nearly upward over the origin, and more in- 
clined as the distance from the origin increases. 

(5.) The shape of the area of disturbance de- 
pends on the nature of the materials through 
which the wave is moving. If these are of 
nearly uniform elasticity in all directions, the 
area is nearly circular; if more elastic in one 
direction than in another, the area is irregular 
in shape. 

52. The Varieties of Earthquake Motion at the 
Earth's Surface are — 

(1.) A wave-like motion, in which the ground 
rises and falls like waves in water. 

(2.) An upward motion, somewhat similar to 
that which follows an explosion of powder below 
the surface. This has been known to occur with 
sufficient force to throw heavy bodies considerable 
distances up into the air. 

(3.) A rotary motion, which, from its destruc- 
tive effects, is fortunately of rave occurrence. 

Humboldt mentions an earthquake that happened in 
Chili where the ground was so shifted that three great 



palm trees were twisted around one another like willow 
wands. 

There are two kinds of movement transmitted through 
the crust during earthquakes: these are the earthquake 
motion proper, and the motion that produces the accompanying 
sounds. 

53. The Velocity of Earthquake Motion varies 
according to the intensity of the shock and the na- 
ture of the material through which it is trans- 
mitted. No average result can therefore be 
given. Various observers have estimated it at 
from 8 to 30 miles per minute. 

54. The Sounds Accompanying Earthquakes 
vary both in kind and intensity. Sometimes 
they resemble the hissing noises heard when red- 
hot coals are thrown into water ; sometimes they 
are rumbling, but more frequently they are of 
greater intensity, and are then comparable to 
discharges of artillery or peals of thunder. 

The confused roaring and rattling are probably caused 
by the different rates of transmission of the sound through 
the air and rocks. 

55. Duration of the Shocks. — When the area 
of disturbance is large, shocks of varying intensity 
generally follow each other at irregular intervals. 
Though, in general, the violence of the shock is 
soon passed, disturbances may occur at intervals 
of days, weeks, or even years. 

During the earthquake in Calabria in 1783, when nearly 
100,000 persons perished, the destructive vibrations lasted 
scarcely two minutes, but the tremblings of the crust con- 
tinued long afterward. During the earthquake at Lisbon 
in 1755, when about the same number perished, the shock 
which caused the greatest damage continued but five or 
six seconds, while a series of terrible movements followed 
one another at intervals during the space of five minutes. 

56. Cause of Earthquakes. — It is generally be- 
lieved that the principal cause of earthquakes is the 
force produced by the contraction of a cooling crust. 

During the cooling of the earth the crust con- 
tinually contracts, and the pressure so produced, 
slowly accumulating for years, at last rends it 
in vast fissures, thus producing those violent 
movements of its crust called earthquakes. If 
this theory be admitted — and it is a probable one 
— the earth's crust must every now and then be 
in such a strained condition that the slightest 
increase of force from within, or of diminished 
resistance from without, would disturb the con- 
ditions of equilibrium, and thus result in an 
earthquake. 

57. Strain Caused by Contraction consequent on 
cooling is well exhibited in the so-called "Prince Ru- 
pert's Drops," which are made by allowing melted glass 
to fall in drops through cold water. The sudden cooling 



of the outside produces powerful forces, which tend to 
compress the drop; but, since these forces balance one 
another, no movement occurs until, by breaking off the 
long end of the drop, one set of forces is removed, when 
the others, no longer neutralized, tear the drop into almost 
countless pieces. 

Similar effects are produced by unequal contraction and 
expansion. Hot water poured into a tumbler will often 
crack it. The crackling sound of a stovepipe when sud- 
denly heated or cooled is a similar effect. 

58. Other Causes of Earthquakes. — Earth- 
quakes may also be occasioned by — 

(1.) The sudden evolution of gases or vapors 
from the pasty interior. 

This is probably the cause of many of the 
slight shocks that occur in the neighborhood of 
active volcanic regions. 

(2.) Shocks caused by falling masses. 

Those who deny the existence of a pasty interior, en- 
deavor to explain the production of earthquakes by the 
shock caused by the occasional caving in of huge masses 
of rocks, in caverns hollowed out by the action of subter- 
ranean waters ; or by the gradual settling of the upturned 
strata in mountainous districts. There can be no doubt 
that even moderately severe shocks are caused by falling 
masses ; but such a force is utterly inadequate to produce 
a shock like that which destroyed Lisbon, when an area 
of nearly 7,500,000 square miles was shaken. 

59. Periodicity of Earthquakes. — It was for- 
merly believed that earthquakes occurred with- 
out any regularity, but by a comparison of the 
times of occurrence of a great number it has been 
discovered that they occur more frequently — 

(1.) In winter than in summer ; 

(2.) At night than during the day ; 

(3.) During the new and full moon, when the 
attractive force of the sun and moon acts simul- 
taneously on the same parts of the earth. 

Earthquake shocks are more frequent in winter, 
and during the night, because the cooling, and 
consequent contraction, occur more rapidly at 
these times, and therefore the gradually accumu- 
lating force is more apt to acquire sufficient inten- 
sity to rend the solid crust. 

Earthquakes are more frequent during new 
and full moon, because the increased force on 
the earth's crust caused by the position of the 
sun and moon at these times, is then added to 
the accumulated force produced by cooling. 

It has been asserted that in the equatorial regions earth- 
quakes are especially frequent during the setting in of 
periodical winds called the monsoons, at the change of 
the rainy season or during the prevalence of hurricanes. 
These facts, however, are not well established. 

60. Distribution of Earthquakes. — Earth- 
quakes may occur in any part of the world, but 



30 



PHYSICAL GEOGRAPHY. 



are most frequent in volcanic districts. They are 
more frequent in mountainous than in flat coun- 
tries. They are especially frequent in the high- 
est mountains. According to Huxley, fairly pro- 
nounced earthquake shocks occur in some part of 
the earth at least three times a week. 

There is, in many instances, an undoubted connection 
between volcanic eruptions and earthquakes. Humboldt 
relates that during the earthquake at Eiobamba, when 
some 40,000 persons perished, the volcano of Pasto ceased 
to emit its vapor at the exact time the earthquake began. 
The same is related of Vesuvius at the time of the earth- 
quake at Lisbon. 

61. Phenomena of Earthquakes. — In order to give 
some idea of the phenomena by which severe earthquake 
shocks are attended, we append a brief description of the 
earthquake which destroyed the city of Lisbon, on the 1st 
of November, 1755. The loss of life on this occasion was 
the more severe, since the shock occurred on a holy day, 
when nearly the whole population was assembled in the 
churches. A sound like thunder was heard, and, almost 
immediately afterward, a series of violent shocks threw 
down nearly every building in the city. Many who es- 
eaped the falling buildings perished in the fires that soon 
kindled, or were murdered by lawless bands that after- 
ward pillaged the city. 

The ground rose and fell like the waves of the sea ; huge 
chasms were opened, into which many of the buildings 
were precipitated. In the ocean a huge wave, over 50 feet 
high, was formed, which, retreating for a moment, left the 
bar dry, and then rushed toward the land with frightful 
force. This was repeated several times, and thousands 
perished from this cause alone. The neighboring moun- 
tains, though quite large, were shaken like reeds, and 
were rent and split in a wonderful manner. 

This earthquake was especially remarkable for the im- 
mense area over which the shock extended. It reached 
as far north as Sweden. Solid mountain-ranges — as, for 
example, the Pyrenees and the Alps — were severely shaken. 
A deep fissure was .opened in France. On the south, the 
earthquake waves crossed the Mediterranean and destroyed 
a number of villages in the Barbary States. On the west, 
the waves traversed the bed of the Atlantic, and caused 
unusually high tides in the West Indies. In North Amer- 
ica the movements were felt as far west as the Great Lakes. 
Feebler oscillations of the ground occurred at intervals for 
several weeks after the main shock. 

62. Non-volcanic Igneous Eruptions. — In re- 
gions remote from volcanoes, melted rock has 
been forced up from the interior through fissures 
in the rocks of nearly all geological formations. 
On cooling, the mass forms what is called a dyke. 
Dykes vary in width from a few inches to several 
yards. They are generally much harder than the 
rocks through which they were forced, and, being 
less subject to erosion, often project considerably 
above the general surface. 

From their mode of formation, dykes are gen- 
erally without traces of stratification, but by cool- 
ing a series of transverse fractures are sometimes 



produced. The dykes thus obtain the appearance 
of a series of columns, called basaltic columns. 

Igneous rocks of this description are found in 
all parts of the continents, but are especially com- 
mon near the borders of mountainous districts. 
Fingal's Cave, in Scotland, is a noted example 
of basaltic columns. 




HE™ 




Fig. 24. Basaltic Columns, Fingal's Cave, Scotland, 

63. Gradual Elevations and Subsidences. — Be- 
sides the sudden changes of level produced by 
earthquakes, there are others that take place 
slowly, but continuously, by which large portions 
of the surface are raised or lowered from their 
former positions. The rate of movement is very 
slow — probably never exceeding a few feet in a 
century. The following examples are the most 
noted : 

The Scandinavian peninsula (Norway and Swe- 
den) is slowly rising in the north and sinking in 
the soidh. 

The southern part of the coast of Greenland is 
sinking. 

The North American coast, from Labrador to 
New Jersey, is rising. 

The Andes Mountains, especially near Chili, 
are gradually rising. 

The Pacific Ocean, near the centre, is sinking 
over an area of more than 6000 miles. 

The cause of these movements is to be traced 
to the warping action caused by gradual contrac- 
tion of a cooling crust. 



SYLLABUS. 



31 



SYLLABUS. 



The earth was originally melted throughout. It after- 
ward cooled on the surface and formed a crust. The earth's 
original fluidity is rendered probable — 

(1.) By the spherical shape of the earth; 

(2.) By the crystalline rocks underlying all others; 
and 

(3.) By the greater heat of the earth during geological 
time. 

The interior is still in a highly-heated condition. This 
is proved — 1st. By the increased heat of the crust as we go 
below the surface ; 2d. By the escape of lava from volca- 
noes in all latitudes. 

The following opinions are held concerning the condi- 
tion of the interior of the earth : 

(1.) That the earth has a solid centre and crust, with a 
heated layer between. 

(2.) That the earth has a solid crust only, and an inte- 
rior sufficiently heated to be in a fused or in a pasty con- 
dition. 

(3.) That the earth is solid throughout, but highly 
heated in the interior. 

The thickness of the crust is not known. It is probable 
that the portions solidified by cooling pass insensibly into 
those that are nearly solid from the combined influence 
of loss of heat and increasing pressure. The heated 
interior, however, must lie comparatively near the sur- 
face. 

The effects produced by the heated interior on the crust 
are — 1st. Volcanoes; 2d. Earthquakes; 3d. Non-volcanic 
igneous eruptions; and 4th. Gradual elevations or subsi- 
dences. 

Volcanic mountains are of a variety of shapes. Near 
their craters the cone shape predominates, and serves to 
distinguish these mountains as a class. 

The ejected materials of volcanoes are — 1st. Melted rock 
or lava ; 2d. Ashes or cinders ; 3d. Vapors or gases. 

These materials are brought up from great depths into 
the volcanic mountain by the force produced by a contract- 
ing globe. They may escape from the crater — 1st. By the 
pressure of highly-heated vapors ; or, 2d. By the pressure 
of a column of melted lava. 

The inclination of the slopes of the volcanic cone de- 
pends on the materials of which it is composed. Ash- 
cones are steeper than those formed of lava. 

Eruptions are of two kinds, explosive and non-explo- 
sive. 

High volcanic mountains are, as a rule, characterized by 
non-explosive eruptions. 

Volcanoes occur both on the surface of the land and on 
the bed of the ocean. 

Those on the land occur mainly near the borders of 
sinking oceans, where the crust is weakest. 

The principal volcanic districts of the world are — 1. 
Along the shores of the Pacific ; 2. On the islands which 
are scattered over the Pacific; 3. Scattered over the seas 
which divide the northern and southern continents ; 4. In 
the northern and central parts of the Atlantic Ocean ; 5. 
In the western and central parts of the Indian Ocean. 

The centres of volcanic activity are found in the An- 
tilles and in the Sunda Islands, where several lines of 
fracture cross each other. 



Subordinate volcanic phenomena are seen in — 1. Mud 
volcanoes; 2. Solfataras; 3. Geysers. 

Earthquakes are shakings of the earth's crust ; they may 
occur with or without a permanent displacement. 

The following facts have been discovered as to earth- 
quakes : 

(1.) Their place of origin is not very deep-seated. 

(2.) The area of disturbance increases with the energy 
of the shock and the depth of the origin. 

(3.) The shape of the origin is that of a line, and not 
that of a point. 

(4.) The shape of the area of disturbance depends on 
the elasticity of the materials through which the shock 
moves. 

(5.) The earthquake motion travels through the earth 
as spherical waves which move outward in all directions 
from the origin of the disturbance. 

The movement at the earth's surface may be — 1st. In 
the form of a gentle wave ; 2d. An upward motion ; 3d. A 
rotary motion. 

The velocity with which the earthquake motion is trans- 
mitted varies with the intensity of the shock and the 
nature of the materials through which it is propagated. 

There are two distinct kinds of motion accompanying 
earthquake waves : the earthquake motion proper, and 
the motion producing the accompanying sounds. 

As a rule, the earthquake shocks which produce the 
greatest damage are of but short duration, generally but 
a few seconds or minutes. Slighter disturbances may fol- 
low the main shock at intervals of days, weeks, or even 
years. 

Earthquake shocks are more frequent — 1st. In winter 
than in summer ; 2d. At night than during the day ; 3d. 
During the time of new and full moou than at any other 
phase. 

Earthquakes are mainly caused by the gradually in- 
creasing force produced by the contraction of the crust. 

Earthquakes are also to be attributed to the forces which 
eject the molten matter from the craters of volcanoes. 

Slight earthquake shocks may be occasioned by the fall- 
ing in of masses of rock from the roofs of subterranean 
caverns, or by the settling of upturned strata. 

Earthquakes may occur in any part of the earth, but are 
most frequent in volcanic and in mountainous regions. 

Dykes are masses of rock formed by the gradual cooling 
of melted matter which has been forced up through fis- 
sures from the interior. 

Basaltic columns are formed by dykes. They owe their 
columnar structure to fractures produced on cooling. 

The crust of the earth is subject to gradual as well as to 
sudden changes of level. 

The Scandinavian peninsula is rising on the north and 
sinking on the south. 

The southern coast of Geeenland is sinking. 

The North American coast, from Labrador to New Jer- 
sey, is rising. 

The range of the Andes near Chili is rising. 

The bed of the Pacific in the neighborhood of the Poly- 
nesian island chain is sinking. 

These moTemieaits are caused by the contraction of a 
cooling crust. 



32 



PHYSICAL GEOGRAPHY. 



REVIEW QUESTIONS. 



o>»<o 



The Heated Interior. 

Enumerate the proofs that the interior of the earth is 
still in a highly-heated condition. 

Name some circumstances which render it probable that 
the earth was originally melted throughout. 

What is the average rate of increase of temperature 
■with descent below the surface? 

How can it be shown that the whole interior of the 
earth is filled with highly-heated matter? 

Why is it so difficult to assign a definite limit to the 
thickness of the earth's crust? 

Is the interior of the earth supposed to be in as fluid a 
condition as that of the lava which escapes from a volcano ? 

What four classes of effects are produced in the crust by 
the heated interior ? 

Volcanoes. 

What are volcanoes ? What connection have they with 
the interior of the earth? How do active volcanoes differ 
from those which are extinct ? 

Explain the origin of the conical form of volcanic 
mountains. 

Which generally produces the more destructive effects, 
ashes or lava? Why? 

Enumerate the materials which are ejected from the in- 
terior of the earth through the craters of volcanoes. 

What is tufa ? How is it formed ? 

Which has the greater inclination, a lava-cone or an 
ash-cone ? 

Explain in full the manner in which the shrinkage, or 
contraction of the earth on cooling, produces a pressure 
both in the interior and in the crust. 

By what forces are volcanic eruptions produced ? 

Into what two classes may all volcanic eruptions be di- 
vided ? How are those of each class caused ? 



Give an example of each of these classes. 

What is the highest volcano in the world? 

Under what five regions may all the volcanoes in the 
world be arranged? 

In what parts of the world are volcanoes most numer- 
ous? 

Why are volcanoes more numerous here than elsewhere? 

Name some of the regions of submarine volcanoes. 

Why are all volcanoes found near the coasts of the con- 
tinents or on islands ? 

What are mud volcanoes ? Solfataras ? 

Earthquakes. 

What are earthquakes ? Into what two classes may they 
be divided ? 

Name some facts that have been discovered about earth- 
quakes. 

Name three kinds of earthquake motion. Which is the 
most dangerous ? 

Describe the sounds which accompany earthquakes. 

What is the main cause of earthquakes ? To what other 
causes may they be attributed? 

What facts have been discovered respecting the period- 
icity of earthquakes? 

Give a short description of the earthquake which de- 
stroyed the city of Lisbon. 

Are any portions of the earth free from earthquake 
shocks ? 

In what parts of the earth are earthquake shocks most 
frequent ? 

What are dykes ? How were they formed ? 

Enumerate some of the gradual changes of level which 
are now occurring in the crust of the earth. By what are 
these changes caused ? 



MAP QUESTIONS. 



oXKo 



Trace on the map the five principal volcanic districts of 
the earth. 

Which contains the greater number of volcanoes, the 
Atlantic or the Pacific shores of the continents? 

Does the eastern or the western border of the Indian 
Ocean contain the greater number of volcanoes? 

Name the principal volcanic islands of the Atlantic. 
Of the Indian. Of the Pacific. 

Locate the following volcanoes : Hecla, Pico, Kilauea, 
Sarmiento, Llullayacu, Egmont, Cosiguina, Teneriffe, 
Antisana, Kilimandjaro, Demavend, Peshan, Osorno, Ere- 
bus, and Terror. 

Name the principal volcanic mountains of North America. 



In what part of the Atlantic Ocean are submarine erup- 
tions especially frequent 1 

Name three noted volcanoes of the Mediterranean 
Sea. 

Name the portions of the earth which were shaken by 
the earthquake of Lisbon. When did this earthquake 
occur? 

What noted volcanoes are found in the region visited by 
the earthquake of Lisbon ? 

In what portions of the Eastern Hemisphere are earth- 
quake shocks especially frequent? In what portions o1 
the Western Hemisphere? 




THE CRUST OF THE EARTH. 



33 



Section II. 

THE OUTSIDE OF THE EARTH. 



►oXKo 



CHAPTER I. 

The Crust of the Earth. 

64. Composition of the Crust. — The elementary 
substances are not equally distributed throughout 
the earth's crust. Many of these substances occur 
only in extremely small quantities, while others 
are found nearly everywhere. 

Although the deepest cutting through the earth's crust 
does not extend vertically more than about two miles be- 
low the level of the sea, yet the upturning of the strata, or 
the outcropping of the different formations, enables us to 
study a depth of about sixteen miles of the earth's crust. 

A careful study of the composition of this part of the 
crust shows that oxygen constitutes nearly one-half of it, 
by weight. Silicon, an element which, when combined 
with oxygen, forms silica or quartz, constitutes, either as 
sand, or combined with various bases as silicates, one- 
fourth; so that these two elements form at least three- 
fourths, by weight, of the entire crust. The following are 
also prominent ingredients of rocks — aluminium, which, 
when combined with oxygen, forms alumina, the basis of 
clay : magnesium, calcium, potassium, sodium, iron, and car- 
bon. These nine substances, according to Dana, form 
^^jths, by weight, of the entire crust. 

Sulphur, hydrogen, chlorine, and nitrogen also occur fre- 
quently. The remaining elements are of comparatively 
rare occurrence. 

65. The Origin of Rocks. — When the earth was 
yet a melted globe, the water which now covers 
the larger portion of its surface hung over it, 
uncondensed, either as huge clouds or as masses 
of vapor. After a comparatively thin crust had 
formed, the vapor was condensed as rain, and cov- 
ered the earth with a deep layer of boiling water. 
Occasionally the cooling crust was broken by the 
increasing tension, and portions of the molten in- 
terior were forced out and spread over the sur- 
face. The muddy waters then cleared by depos- 
iting layers of sediment over the ocean's bed. 

When, by long-continued cooling, the crust be- 
came thicker, the breaking out of the interior oc- 
curred less frequently, and contraction, wrinkling 
the surface in huge folds, caused portions to 
emerge from the ocean and form dry land. Dur- 
ing all this time the waters were arranging the 
looser materials in layers or strata which were 



originally more or less horizontal ; but wher- 
ever the contraction forced the melted interior 
through the crust or upturned it in huge folds, 
the horizontal position of the deposits was de- 
stroyed ; and even when not so disturbed, the 
heat of the interior, escaping through fissures, 
often produced such alterations as to confuse or 
completely to obliterate all traces of their regu- 
lar bedding. 

The almost inconceivable extent of geological time may 
be inferred from the calculations of He.lmholtz, based on 
the rapidity of the cooling of lava. These calculations 
show that in passing from a temperature of 2000° C. to 
200° C. a time equal to three hundred and fifty million years 
must have elapsed. Before this a still greater time must 
have elapsed, and after it came the exceedingly great ex- 
tent of geological time proper. 

66. According to their Origin, rocks may be 
divided into three distinct classes : 

(1.) Igneous Rocks, or those ejected in a melted 
condition from the interior, and afterward cooled. 

(2.) Aqueous Rocks, or those deposited as sedi- 
ment by water. When mineral matter settles in 
water, the coarser, heavier particles reach the bot- 
tom first, so that a sorting action occurs, which 
makes the different layers or strata vary in the 
size and density of their particles, and, to a great 
extent, in their composition. 

Aqueous rocks are sometimes called sediment- 
ary rocks. 

(3.) Metamorphic Rocks, or those originally 
deposited in layers, but afterward so changed by 
the action of heat as to lose all traces of stratifi- 
cation. 

This change, which is called metamorphism, is caused by 
heat acting under pressure in the presence of moisture. Under 
these conditions a far less intense heat is required to re- 
move all traces of stratification. Metamorphism appears 
to consist mainly in a rearrangement of the chemical con- 
stituents of the rocks. 

67. According to their Condition, rocks may 
be divided into two classes: 

(1.) Stratified Rocks, or those arranged in 
regular layers. Aqueous rocks are always strati- 
fied, and sometimes, though rarely, metamorphic 
rocks are stratified. 



34 



PHYSICAL GEOGRAPHY. 




Fig. 25. Stratified Eock. 

In Fig. 25 the different layers or strata are shown by 
the shadings. Stratified rocks are the most common form 
of rocks found near the earth's surface. 

Stratified l'ocks are largely composed of fragments of 
older rocks; for this reason they are sometimes called 
fragmental rocks. 

(2.) TJnstratified Rocks, or those destitute of 
any arrangement in layers. They are of two kinds : 

(1 .) Igneous, or those which were never stratifi ed. 

(2.) Metamorphic, or those which were once 
stratified, but have lost their stratification by 
the action of heat. 

Unstratified rocks are sometimes called crystal- 
line rocks, because they consist of crystalline 
particles. 

68. Fossils are the remains of animals or plants 
which have been buried in the earth by natural 
causes. Generally, the soft parts of the organism 
have disappeared, leaving only the harder parts. 
Sometimes the soft parts have been gradually re- 
moved, and replaced by mineral matter, generally 
lime or silica; thus producing what are called 
petrifactions. At times the mere impression of 
the animal or plant is all that remains to tell 
of its former existence. 




Fig. 26. Fossil Enorinite. 



When the remains of an animal or plant are exposed to 
the air or buried in dry earth, they generally decompose 
and pass off almost entirely as gases ; but when buried 
under water or in damp earth, their preservation is more 
probable. Therefore, the species most likely to become 
fossilized are those living in water or marshes, or in the 
neighborhood of water or marshes. 

69. According to the Presence or Absence of 
Fossil Remains, rocks may be divided into two 
classes : 



(1.) Fossiliferous Rocks, or those which con- 
tain fossils. They are stratified and are of 
aqueous origin. Metamorphic rocks, in very 
rare instances, are found to contain fragments 
of fossils. 

(2.) Non-fossiliferous Rocks, or those destitute 
of fossils. They include all igneous rocks and 
most of those that are metamorphic. 

70. Palaeontology is the science which treats of fossils. 

Palaeontology enables us to ascertain the earth's condi- 
tion in pre-historic times, since by a careful examination 
of the fossils found in any rocks we discover what animals 
and plants lived on the earth while such rocks were being 
deposited. The earth's strata thus become the pages of a 
huge book; and the fossils found in them, the writings 
concerning the old life of the world. By their careful 
study geologists have been enabled to find out much of 
the earth's past history. 

71. Division of Geological Time. — A compari- 
son of the various species of fossils found in the 
earth's crust discloses the following facts : 

(1.) The fossils found in the lowest rocks bear 
but a slight resemblance to the animals and 
plants now living on the earth. 

(2.) The fossils found in the intermediate strata 
bear a resemblance to existing species, though 
this resemblance is not so strongly marked as in 
the upper strata. 

(3.) The fossils found in the upper strata bear 
a decided resemblance to existing species. 

It is on such a basis that the immense extent 
of geological time is divided into the following 
shorter periods or times: 

(1.) Archaean Time, or the time which wit- 
nessed the dawn of life. This time included an 
extremely long era, during most of which the con- 
ditions of temperature were such that no life could 
possibly have existed. Toward its close, however, 
the simplest forms of life were created. 

The lower Archaean rocks resulted from the 
original cooling of the molten earth, and cover 
its entire surface, including the floor of the ocean. 
On these rest less ancient Archaean rocks, formed 
as sedimentary deposits of the older rocks. 

The rocks of the Archaean Time in North America in- 
clude the Laurentian, the lowest, named from the river 
St. Lawrence, near which they occur, and the Huronian, 
named from their occurrence near Lake Huron. 

(2.) Palaeozoic Time, or ancient life, included 
the time during which the animals and plants 
bore but little resemblance to those now living. 

(3.) Mesozoic Time, or middle life, included 
the time during which the animals and plants 
began to resemble those now living. 



(4.) Cenozoic Time, or recent life, included the 
time during which the animals and plants bore 
decided resemblance to those now living. 

These times are divided into ages. 

Archaean Time includes — 

(1.) The Azoic Age; 

(2.) The Eozoic Age. 

Palaeozoic Time, or, as it is sometimes called, 
the Primary, includes — 

(1.) The Age of Invertebrates, or the Silurian ; 

(2.) The Age of Fishes, or the Devonian ; 

(3.) The Age of Coal-plants, or the Carbon- 
iferous. 

Mesozoic Time, or, as it is sometimes called, 
the Secondary, includes the Age of Reptiles. 

Cenozoic Time includes — 

(1.) The Tertiary, or the Age of Mammals ; 

(2.) The Quaternary, or the Age of Man. 

Where no disturbing causes existed, and the 
land remained under the seas, the rocks deposited 
during these periods were thrown down in regu- 
lar strata, one over the other. The Archaean 
were the lowest ; above them were the Palaeozoic, 
then the Mesozoic, and finally those of the Ceno- 
zoic. Generally, however, frequent dislocations 
of the strata have disturbed the regular order 
of arrangement. 

72. The Azoic Age included all the time from 
the first formation of the crust to the appearance 
of animal and vegetable life. 

The Eozoic Age is that which witnessed the 
dawn of life. The sedimentary rocks of this age 
are so highly metamorphosed that nearly all traces 
of life have been obliterated. Among plants, the 
marine alga, or sea-weeds, and among animals, 
the lowest forms of the protozoa, were probably 
the chief species. 

73. The Age of Invertebrates, or the Silurian, 
is sometimes called the Age of Mollusks. Among 
plants, alga, or sea-weeds, are found ; among ani- 
mals, "protozoa, radiates, articulates, and mollusks, 
but no vertebrates. Hence the name, Age of In- 
vertebrates. Mollusks were especially numerous. 

The name Silurian is derived from the ancient Silures, 
a tribe formerly inhabiting those parts of England and 
Wales where the rocks abound. 

74. The Age of Fishes, or the Devonian. — 
During this age all the sub-kingdoms of animals 
are found, but the vertebrates first appear, being 
represented by fishes, and from this fact the name 
has been given to the age. Land-plants are also 
found. Immense beds of limestone and red sand- 
stone were deposited. 

5 



The name Devonian is derived from the district of Dev- 
onshire, England, where the rocks abound. 

75. The Age of Coal-Plants, or the Carbonif- 
erous. — The continents during this age consisted 
mainly of large, flat, marshy areas, covered with 
luxuriant vegetation, subject, at long intervals, to 
extensive inundations. The decaying vegetation, 
decomposing under water, retained most of its 
solid constituent, carbon, and formed beds of coal. 
All the sub-kingdoms of animals were represented 
and reptiles also existed. The comparatively few 
land-plants of the preceding age now increased 
and formed a dense vegetation. 

To favor such a luxuriant vegetation the air 
must have been warm and moist. Since all the 
coal then deposited previously existed in the air 
as carbonic acid, the Carboniferous Age was nec- 
essarily characterized by a purification of the 
atmosphere. 




Pig, 27. Carboniferous Landsoape, (A restoration.) 

Formation of Coal. — In every 100 parts of dry vege- 
table matter there are about 49 parts of carbon, 6 of hydro- 
gen, and 45 of oxygen. The carbon is a solid ; the hydro- 
gen and oxygen are gases. It is from the carbon that coal 
is mainly formed. When the decomposition of the vege- 
table matter takes place in air, the carbon passes off with 
the hydrogen and oxygen as various gaseous compounds ; 
but when covered by water, most of the carbon is retained, 
together with part of the oxygen and hydrogen. Although 
every year our forests drop tons of leaves, no coal results, 
the deposit of one year being almost entirely removed 
before that of the next occurs. 

It has been computed that it would require a depth of 
eight feet of compact vegetable matter to form one foot of 
bituminous coal, and twelve feet of vegetable matter to 
form one foot of anthracite coal. Anthracite coal differs 



36 



PHYSICAL GEOGRAPHY. 



from bituminous mainly in the greater metamorphism to 
which it has been subjected ; it contains a greater propor- 
tion of carbon and less hydrogen and oxygen. 

76. The Age of Reptiles. — In this age the ani- 
mals and plants begin to resemble existing species. 
The age is characterized mainly by the prepon- 
derance of reptiles, many of which were very 
large, as, for example, the plesiosaurus, an animal 
with a long, snake-like neck and a huge body, or 
the ichthyosaurus, with a head like a crocodile and 
short neck and large body. Both of these ani- 
mals were furnished with fin-like paddles, and 
lived in the water. Huge pterodactyls, or bat- 
like saurians, flew in the air or paddled in the 
water. Mammals and birds also occur. 




Fig, 28. The Age of Reptiles. (A restoration.) 

77. The Age of Mammals, or the Tertiary Age. 

— Mammals, or animals that suckle their young, 
occurred in great numbers, and, being the highest 




Fig. 29. Mastodon giganteus. An Animal of the Mammalian Age 

type of life, gave the name to the age. The ani- 
mals and plants of the Mammalian Age closely 
resembled existing species, though most of them 
were much larger ; as, for example, the dinothe- 



rium, a huge animal, with a trunk like an ele- 
phant, but with downward-turned tusks ; the 
palceotherium, and many others. 

78. The Era of Man, or the Quaternary Age, 
witnessed the introduction of the present animate 
and plants and the creation of man. 

79. Changes Now Occurring in the Earth's 
Crust. — Geological time was characterized by ex- 
tensive changes, both in the kind and luxuriance 
of life, and in the nature of its distribution. 

The earth is still undergoing extensive changes, 
which are caused by the following agencies : 

(1.) By the Winds, which often carry sand 
from a desert and distribute it over fertile plains : 
in this manner the narrow tract of fertile land on 
the borders of the Nile, in Egypt, receives much 
sand from the Sahara. The winds are also piling 
up huge mounds of sand along the sea-coasts, 
forming what are called dunes, or sandhills. 

(2.) By the Moisture of the Atmosphere, soak- 
ing into porous rocks or running into the crevices 
between solid ones. This water in freezing ex- 
pands with force sufficient to rend the rock into 
fragments, which are carried away by the rivers 
or, when sufficiently small, by the winds. 

(3.) By the Action of Running Water. — Rivers 
wash away portions of their banks or cut their 




Fig. 30. Cnrions Effect of Erosion. 

way through their channels. This action is 
called erosion. It occurs even in the hardest 



DISTRIBUTION OF THE LAND-AREAS. 



37 



rocks. The materials thus carried away are 
spread over the lowlands near the mouth of the 
river or thrown into the sea, where they often 
form large deposits. By the constant action of 
these causes the mean heights of the continents are 
decreasing and their breadths increasing. 

The most remarkable instance of erosion is 
found in the canons of the Colorado Biver, where 
the waters have eaten a channel through the hard 
limestones and granites that form the bed of the 
stream, until they now run through gorges whose 
walls ascend almost perpendicularly to the height 
of from 3000 to 6000 feet. 

A good idea of this great depth may be obtained by 
walking along a straight street for about a mile (5280 
feet), and then imagining the street set upright in the air. 
On looking down toward the starting-place, we would see 
it as it would appear at the bottom of a hole about 6000 
feet deep. 

The forms produced by erosion are often extremely fan- 
tastic. Tall, slender, needle-like columns, capped by a 
layer of harder rock, sometimes occur, thus showing in a 
marked manner an effect of erosion. 

(4.) By the Action of Ocean Waves, changing 
the outlines of coasts ; as may be seen in portions 
of the coasts of England and Scotland. 

(5.) By the Agency of Man, witnessed mainly 
in the destruction of the forests over extended 
areas. 

(6.) By the Contraction of a Cooling Crust, 
resulting in — 1. Earthquakes; 2. Volcanoes; 3. 
Gradual uplifts and subsidences. 



ot»jo 



CHAPTER II. 
Distribution of the Land-Areas. 

80. Geographic Effects of Light, Heat, and 
Moisture. — The peculiarities observed in the dis- 
tribution of animal and vegetable life are caused 
by differences in the distribution of light, heat, 
and moisture. Since light, heat, and moisture 
are influenced by the interaction of land, water, 
and air, we must first study the distribution and 
grouping of these inorganic or dead forms before 
we can understand those that are living. 

81. The Distribution of the land.— Of the 
197,000,000 square miles that make up the 
earth's surface, about 144,000,000 are water and 
53,000,000 land. The proportion is about as the 
square of 5 is to the square of 3. If, therefore, 
we erect a square on a side of five, its entire area 
will represent the relative water-area of the globe ; 



while a square whose side is three will represent 
the relative land-area. 



" — — ,Watek-Aeea, = -f 

=^ E=£r^ =Tl44i500,000 square miles.; 




: 53,000,000 square miles. 




Fig. 31. Eelative Land- and Water-Areas. 

82. The Distribution of the Land can be best 
studied when arranged under two heads : 

(1.) The Horizontal Forms of the Land, or the 
different shapes produced in the land-areas by the 
coast lines, or by the contact of land and water ; 

(2.) The Vertical Forms of the Land, produced 
by the irregularity of the surface of the high 
lands and low lands. 

83. The Horizontal Forms. — The land-areas 
are divided into continents and islands. 

The Eastern Hemisphere contains four conti- 
nents : Europe, Asia, Africa, and Australia. The 
first three form one single mass, which is called 
the Eastern Continent. 

Though the word "continent" strictly refers to an ex- 
tended area of land entirely surrounded by water, usage 
has sanctioned the application of the term to the grand 
divisions of the land. It is quite correct, therefore, to 
speak of the North American Continent, the Asiatic Con- 
tinent, etc. 

The Western Hemisphere contains two conti- 
nents : North and South America ; these consti- 
tute what is called the Western Continent. 

The following are the extremities of the conti- 
nents : 

In the Eastern Continent- 
Host northern point, Cape Chelyuskin, lat. 78° 16' N. 

Most southern point, Cape Agulhas, lat. 34° 51' S. 

Most eastern point, East Cape, long. 170° W. 

Most western point, Cape Verd, long. 17° 34' W. 

In the Western Continent — 

Most northern point. Point Barrow, lat. 72° N. 

Most southern point, Cape Froward, lat. 53° 53' S. 

Most western point, Cape Prince of Wales, long. 168° W. 

Most eastern point, Cape St. Eoque, long. 35° W. 



38 



PHYSICAL GEOGRAPHY. 



84. Peculiarities in the Distribution of the 
Land: 

(1.) The continents extend farther to the north 
than to the south. 

(2.) The land masses are crowded together near 
the north pole, which they surround in the shape 
of an irregular ring. 

(3.) The three main southern projections of 
the land — South America, Africa, and Australia 
— are separated from each other by extensive 
oceans. 

85. Land and Water Hemispheres. — The ac- 
cumulation of the land in the north and its sepa- 
ration in the south lead to a curious result — nearly 
all the land is collected in one hemisphere. 

If one point of a pair of compasses be placed at 
the north pole of a globe, and the other stretched 
out to reach to any point on the equator, they 
will describe on the surface of the globe a great 
circle, and consequently will divide the globe into 
hemispheres. If, while they are stretched this dis- 
tance apart, one of the points be placed at about 
the city of London, a circle swept with the other 
point will divide the earth into land and water 
hemispheres. Such a great circle would pass 
through the Malay Peninsula and the coast of 
Peru. 

The Land Hemisphere contains all of North 
America, Europe, and Africa, and the greater part 
of South America and Asia. The Water Hemi- 
sphere contains the southern portions of South 
America, the Malay Peninsula, and Australia. 




Pig. 32, Land and Water Hemispheres. 

86. Double Continents. — The six grand divis- 
ions or continents may be divided into three pairs, 
called Double or Twin Continents. 

Each Double Continent consists of a northern 
and southern continent, almost separated from 
each other, but connected by a narrow isthmus 
or island chain. 

The three double continents are North and 
South America, Europe and Africa, and Asia 



and Australia. There are, therefore, three north- 
ern and three southern continents. 

The northern continents lie almost entirely in 
temperate latitudes, while the southern lie mainly 
in the tropics. 

87. Lines of Trend. — The study of any map 
of the world on a Mercator's projection will dis- 
close the following peculiarities in the earth's 
structure : 

There are two great systems of courses, trends, or 
lines of direction, along which the shores of the con- 
tinents, the mountain-ranges, the oceanic basins, and 
the island chains extend. 

These trends extend in a general north-easterly 
and north-westerly direction, and intersect each 
other nearly at right angles. 

North-east Trends. — A straight ruler can be so placed 
along the south-eastern coasts of Greenland and the south- 
eastern coasts of North America that its edge will touch 
most of their shore lines. Its general direction will be 
north-east. 

It can be similarly placed along the south-eastern coast 
of South America, the north-western coast of Africa, and 
most of the western coast of Europe ; along the south- 
eastern coasts of Africa ; the south-eastern coast of Hin- 
dostan ; and along the eastern coast of Asia, without its 
general direction differing much from north-east. 

North-west Trends. — A straight ruler can be so placed 
as to touch most of the western shores of North America 
and part of the western coast of South America; most 
of the western coasts of Greenland, or the north-eastern 
coasts of North America, and part of the western coasts 
of Africa. All these courses are sensibly north-west. 

If placed with one end at the mouth of the Mackenzie 
Eiver, and the other on the south-western extremity of 
Lake Michigan, it will cut nearly all the great lakes in 
Central British America. The direction of the island 
chains of the Pacific Ocean in particular is characterized 
by these two trends, many of the separate islands being 
elongated in the direction of the trend of their chain. 

88. Continental Contrasts. — The main pro- 
longation of the western continent extends in the 
line of the north-western trend, while that of the 
eastern continent extends in the line of the north- 
eastern trend. The axes of the continents, or 
their lines of general direction, therefore, inter- 
sect each other nearly at right angles. 

The western continent extends far north and 
south of the equator, while the eastern lies mainly 
north of the equator. The Western Continent, 
therefore, is characterized by a diversity of cli- 
mates; the Eastern Continent, by a similarity. 
The distribution of vegetable and animal life 
in each continent is necessarily affected by the 
peculiarities of its climate. 

It is from the prevalence of the lines of trend that the 



ISLANDS. 



39 



general shape of the continents is mainly triangular. An 
excellent system of map-drawing has been devised on this 
peculiarity. 

The following peculiarities exist in the coast 
lines of the continents : 

The coast lines of the northern continents are 
very irregular, the shores being deeply indented 
with gulfs and bays, while those of the southern con- 
tinents are comparatively simple and unbroken. 

The continents are most deeply indented near 
the regions where the pairs of northern and south- 
ern continents are nearly separated from each 
other. These regions correspond with the lines of 
great volcanic activity, and appear to be areas over 
which considerable subsidence has occurred. 

The continents differ greatly from one another 
in their indentations. Europe is the most indented 
of all the continents. The area of her peninsulas, 
compared with that of her entire area, is as 1 to 4. 
Asia comes next in this respect, the proportion 
being 1 to 5J, while in North America it is but 
1 to 14. 

The following Table gives in the first column the area 
of each of the continents, in the second the length of coast 
line, and in the third the number of square miles of area 
to one mile of coast line : 



CONTINENTS. 


AREA. 


COAST LINE. 


Sq. m. of 
surface 
fori. m. 
of coast. 




17,500,000 sq. miles. 

12,000,000 " 
8,400,000 " 
6,500,000 " 
3,700,000 " 
3,000,000 " 


35,000 miles. 
16,000 " 
22,800 " 
14,500 " 
19,500 " 
10,000 " 


500 




750 


North America- 
South America... 


368 
449 
190 




300 







Europe has, in proportion to its area, 
About three times as much coast line as Asia. 
About four times as much as Africa. 
About twice as much as North America. 
More than twice as much as South America. 

Europe is the most, and Africa the least, deeply 
indented of the continents. 



CHAPTER III. 

Islands. 

89. Relative Continental and Insular Areas. — 
Of the 53,000,000 square miles of land, nearly 
3,000,000, or about one-seventeenth, is composed 
of islands. 

90. Varieties of Islands. — Islands are either 
continental or oceanic. 

Continental Islands are those that lie near the 



shores of the continents. They are continuations 
of the neighboring continental mountain-ranges 
or elevations, which they generally resemble in 
geological structure. They may, therefore, be re- 
garded as projections of submerged portions of the 
neighboring continents. Continental islands have, 
in general, the same lines of trend as the shores of 
the neighboring mainland. 

Continental islands, as a rule, are larger than oceanic 
islands. This is caused by the shallower water in which 
continental islands are generally situated. Papua and 
Borneo have each an area of about 250,000 square miles; 
either of these islands is more than twice as large as the 
combined areas of Great Britain and Ireland. 

91. American Continental Island Chains. 

(1.) The Arctic Archipelago comprises the 
large group of islands north of the Dominion 
of Canada. It consists of detached portions of 
the neighboring continent. 

(2.) The Islands in the Gulf of St. Lawrence 
and its neighborhood are apparently the northern 
prolongations of the Appalachian mountain-sys- 
tem. 

(3.) The Bahamas lie off the south-eastern coast 
of Florida, to whioh they belong by position and 
structure. Their general trend is north-west. 

(4.) The West Indies form a curved range, 
which connects the peninsula of Yucatan with 
the coast-mountains of Venezuela. Here both 
trends appear, though the north-western pre- 
dominates. 




Fig. 33. West India Island Chain. 
1, Cuba ; 2, Hayti ; 3, Jamaica ; 4, Porto Kico ; 5, Caribbee Islands, 
6, Bahamas. 

(5.) The Aleutian Islands form another curved 
range, which connects the Alaskan Peninsula with 
Kamtchatka ; their general trend is north-east. 
They are connected with the elevations of the 
North American continent. 



40 



PHYSICAL GEOGRAPHY. 



(6.) The Islands west of the Dominion of Can- 
ada and Alaska. These are clearly the summits 
of submerged northern prolongations of the Pa- 
cific coast ranges. 

(7.) The Islands of the Patagonian Archi- 
pelago are the summits of submerged prolonga- 
tions of the Andes of Chili. 

92. Asiatic Continental Island Chains consist 
of a series of curved ranges extending along the 
entire coast, and intersecting each other nearly at 
right angles. 

(1.) The Kurile Islands are a prolongation of 
the Kamtchatkan range. 

(2.) The Islands of Japan extend in a curve 
from Saghalien to Corea. 

(3.) The Loo Choo Islands extend in a curve 
from the islands of Japan to the island of For- 
mosa. 

(4.) The Philippines form two diverging chains, 
which merge on the south into the Australasian 
Island chain. The eastern chain extends to the 
southern extremity of Celebes, and the western 
to that of Borneo. 

The Asiatic chains belong to a submerged mountain- 
range extending from Kamtchatka to the Sunda Islands. 
Their general direction is parallel to the elevations of the 
coast. 

93. The Australasian Island Chain. 

The Australasian Island chain is composed of 
a number of islands extending along curved 
trends over a length of nearly 6000 miles, from 
Sumatra to New Zealand. The islands extend 
along three curved lines, whose general direction 
is north-west. 




Pig. 34. Australasian Island Chain. 
1, Sumatra ; 2, Java ; 3, Sumbawa ; 4, ITlores ; 5, Timor ; 6, Borneo ; 
7, Celebes; 8, Gilolo; 9, Ceram; 10, Papua; 11, Louisiade Archipel- 
ago; 12, New Caledonia; 13, New Zealand; 14, Admiralty Islands; 
15, Solomon's Archipelago; 16, Santa Cruz; 17, New Hebrides. 



The Australasian chain was probably connected with the 
Asiatic continent during recent geological time, and sepa- 
rated from it by subsidence. Its numerous volcanoes and 
coral formations prove that subsidence is still taking 
place. 

94. Peculiarity of Distribution. — The follow- 
ing peculiarity is noticed in the distribution of 
continental islands: 

Each of the continents has an island, or a group 
of islands, near its south-eastern extremity. For 
example, North America has the Bahamas and 
the West Indies ; Greenland has Iceland ; South 
America has the Falkland Islands ; Africa has 
Madagascar ; Asia has the East Indies ; and 
Australia has Tasmania. 

95. Oceanic Islands are those situated far away 
from the continents. They occur either in vast 
chains, which generally extend along one or the 
other of the two lines of trend, or as isolated 
groups. 

Oceanic Island Chains. 

The following are the most important : 

(1.) The Polynesian Chain ; 

(2.) The Chain of the Sandwich Islands ; 

(3.) The Tongan or New Zealand Chain. 









X; 






\ \\ii \ 
\;X\\ 




13 s 


\ 


•\ 


iITVx 




X 






s V 








\x 


X > 


x\ 








""- 


\ < 


X 



Pig, 35. Polynesian Island Chain. 
1, Marquesas; 2, Paumotu ; 3, Tahitian ; 4, Kurutu group; 5, Her- 
vey group ; 6, Samoan, or Navigator's ; 7, Vakaafo group ; 8, Vaitupu ; 
9, Kingsruill ; 10, Kalick ; 11, KadacU ; 12, Carolines; 13, Sandwich. 

The Polynesian Chain consists of a series of 
parallel chains, extending from the Paumotu and 
the Tahitian Islands to the Carolines, the Ralick, 
and the Radack groups. Their general direction 
is north-west; the total length of the chain is 
about 5500 miles. 

The Chain of the Sandwich Islands extends in 
a north-westerly direction. Its length is about 
2000 miles. 

The New Zealand Chain extends north-east as 



far as the Tonga Islands, cutting the Australasian 
chain at right angles. 

96. Isolated Oceanic Islands are mainly of two 
kinds : the Volcanic and the Coral. As a rule, the 
Volcanic islands are high, while Coral islands sel- 
dom rise more than twelve feet above the water. 

Volcanic Islands are not confined to isolated 
groups, but occur also in long chains. The Poly- 
nesian, Sandwich, and New Zealand Chains con- 
tain numerous volcanic peaks. But the high, iso- 
lated oceanic islands are almost always of volcanic 
origin, and, consisting of the summits of subma- 
rine volcanoes, are generally small. Some of the 
Canary and Sandwich Islands, which are of this 
class, rise nearly 14,000 feet above the sea. 

97. Coral Islands, or Atolls, though of a great 
variety of shapes, agree in one particular : 

They consist of a low, narrow rim of coral rock, 
enclosing a body of water called a lagoon. 




Fig. 36, A Coral Island. 

98. Mode of Formation of Coral Islands. — The 
reef forming the island is of limestone, derived 
from countless skeletons of minute polyps that 
once lived beneath the surface of the waters. 
The skeletons, however, are not separate. The 
polyp propagates its species by a kind of bud- 
ding ; that is, a new polyp grows out of the body 
of the old. In this way the skeletons of count- 
less millions of polyps are united in one mass and 
assume a great variety of shapes. 

One of the most common species of reef-forming corals, 
the madrepora, is shown in Fig. 37. Many other forms 
exist. 

The delicate coral structures, together with 
shells from various shellfish, are ground into frag- 
ments by the action of the waves, and by the in- 




Fig, 37. Coral, 

filtration of water containing lime in solution, 
they become compacted into hard limestone, on 
which new coral formations grow. 

The growth of the coral mass is directed up- 
ward, and ceases when low-water mark is reached, 
because exposure to a tropical sun kills the polyps. 
But the action of the waves continues, and the 
broken fragments are gradually thrown up above 
the general level of the water. In this way a reef 
is formed, whose height is limited by the force of 
the waves, and seldom exceeds twelve feet. 

On the bare rock, which has thus emerged, a 
soil is soon formed and a scanty vegetation ap- 
pears, planted by the hardy seeds scattered over 
it by the winds and waves. 

The coral island never affords a very comfortable resi- 
dence for man. The palm tree is almost the only valuable 
vegetable species ; the animals are few and small, and the 
arable soil is limited. Moreover, the island is subject to 
occasional inundations by huge waves from the ocean. 

99. Distribution of Coral Islands. —According 
to Dana, the reef-forming coral polyp is found 
only in regions where the winter temperature 
of the waters is never lower than 68° Fahr. 
Some varieties, however, will grow in colder 
water. Coral islands are confined to those parts 
of tropical waters where the depth does not greatly 
exceed 100 feet, and which are protected from cold 
ocean-currents, from the influence of fresh river- 
waters, muddy bottoms, and remote from active vol- 
canoes, whose occasional submarine action causes 
the death of the coral polyp. Though some coral 
polyps grow in quiet water, the greater part thrive 
best when exposed to the breakers. The groivth is 
therefore more rapid on the side toward the ocean 
than on the side toward the island. 



42 



PHYSICAL GEOGRAPHY. 



Coral islands are most abundant in the Pacific Ocean. 
The following groups contain numerous coral islands: 
the Paumotus, the Carolines, the Radack, the Ealick, 
and the Kingsmill groups, and the Tahitiau, Samoan, 
and Feejee Islands, and New Caledonia. 

In the Indian Ocean the Laccadives and the Maldives are 
most noted. 

In the Atlantic Ocean the West Indies and the Bermudas 
are examples. 

100. Varieties of Coral Formations. — There 
are four varieties of coral formations : 

(1.) Fringing Reefs, or narrow ribbons of coral 
rock, lying near the shore of an ordinary island. 

(2.) Barrier Reefs, which are broader than 
Fringing Reefs, and lie at a greater distance 
from the shore, but do not extend entirely around 
the island. 

A barrier reef off the coast of New Caledonia has a 
length of 400 miles. One extends along the north-eastern 
shore of Australia for over 1000 miles. Barrier reefs are 
not continuous, but often have breaks in them through 
which vessels can readily pass. 

(3.) Encircling Reefs are barrier reefs extend- 
ing entirely around the island. As a rule, en- 
circling reefs are farther from the shores of the 
island than barrier reefs. Tahiti, of the Society 
Islands, is an example of an encircling reef. 

(4.) Atolls. — This name is given to reefs that 
encircle lagoons or bodies of water entirely free 
from islands. 

The varieties of reefs just enumerated mark 
successive steps or stages in the progress of for- 
mation of the coral island. 

When a more careful study of the habits of the reef- 
forming coral polyp disclosed the fact of its inability to 
live in the ocean at greater depths than 100 or 120 feet, 
the opinion, which formerly prevailed, of coral islands 
rising from profound depths, had to be abandoned. The 
idea had its foundation in the fact that a sounding-line, 
thrown into the water near the shore of a coral island, 
almost invariably showed depths of thousands of feet, and 
yet brought up coral rock. In no case, however, did the 
rock contain living polyps. An ingenious hypothesis of 
Darwin, which appears well sustained by the extensive 
observations of Dana and others, explains the great depth 
of coral formations. 

101. Darwin's Theory of Coral Islands. — Ac- 
cording to this distinguished naturalist, the coral 
formation begins near the shore of an island that 
is slowly sinking. If the growth of the reef up- 
ward equals the sinking of the island, the thick- 
ness of the reef is limited only by the time during 
which the operation continues. 

In Fig. 38 is shown, in plan and section, an island with 
elevations A, and B, and river a. The coral island begins 
as a fringing reef somewhere off the coast of an ordinary 
island at c, c, c, when the conditions are favorable. The 




Fig. 38. Growth of a Coral Island. 

coral reef must gradually extend around the island, since its 
growth toward the ocean is soon limited by the increasing 
depth, and toward the shore of the island by the muddy 
waters near the surf and the absence of the breakers. 

Meanwhile, as the island is sinking, the channel sepa- 
rating the reef from the coast increases in breadth. A 
harrier reef is thus formed, which at last completely sur- 
rounds the island, and becomes an encircling reef. The 
higher portions of land, which are still above the waters, 
form islands in the central lagoon. Opposite the mouth 
of the river a, the growth is prevented by the fresh water, 
and a break in the reef is thus produced. These breaks 
are sometimes sufficient to permit a ship to enter the 
lagoon. At last all traces of the old island disappear, and 
its situation is marked by a clear lake, surrounded by a 
narrow rim of coral which follows nearly the old coast 
line. 

A coral island, therefore, is always of an ap- 
proximately circular or oval form, and encloses a 
clear space in the ocean. Extended systems of coral 
formations occurring in any region are a proof of 
subsidence. 



CHAPTER IV. 
Relief Forms of the Land. 

102. By the Forms of Relief of the Land is 
meant the elevation of the land above the mean 
level of the sea. 

The highest land in the world is Mount Ever- 
est, of the Himalayas ; it is 29,000 feet high. 
The greatest depression is the Dead Sea, in Pales- 
tine, which is about 1312 feet below the level of 
the ocean. The sum of these is somewhat less 
than six miles. 

An elevation of six miles is insignificant when 



RELIEF FORMS OF THE LAND. 



43 



compared with the size of the earth. If repre- 
sented on an ordinary terrestrial globe, it would 
be scarcely discernible, since it would project 
above the surface only about the TjVTrtii of the 
diameter. The highest elevations of the earth are 
proportionally much smaller than the wrinkles on 
the skin of an orange. 




Fig. 39. Eelative Height of Mountains. 

If, as in Fig. 39, a sphere be drawn to represent the size 
of the earth, its radius will be equal to about 4000 miles. 
If, now, the line A B be drawn equal to the radius, it 
will represent a height of 4000 miles. One-half this 
height would be 2000 miles; one-half of this 1000, and 
successive halves 500 and 250 miles. An elevation of 250 
miles would not therefore be very marked. 

Although the irregularities of the surface are 
comparatively insignificant, they powerfully affect 
the distribution of heat and moisture, and conse- 
quently that of animal and vegetable life. An 
elevation of about 350 feet reduces the tempera- 
ture of the air 1° Fahr. — an effect equal to a 
difference of about 70 miles of latitude. High 
mountains, therefore, though under the tropics, 
may support on their higher slopes a life similar 
to that of the temperate and the polar regions. 

103. The Relief Forms of the Land are divided 
into two classes : 

Low Lands and High Lands. 

The boundary-line between them is taken at 
1000 feet, which is the mean or average elevation 
of the land. 

Low Lands are divided into plains and hills. 

High Lands are divided into plateaus and 
mountains. 

If the surface is comparatively flat or level, it 
is called a plain when its elevation above the sea 
is less than 1000 feet, and a plateau when its ele- 
vation is 1000 feet or over. 
6 



If the surface is diversified, the elevations are 
called hills when less than 1000 feet high ; and 
mountains when 1000 feet or over. 

104. Plains and Hills cover about one-half of 
the land surface of the earth. In the Eastern 
Continent they lie mainly in the north; in the 
Western, they occupy the central portions. 

Plains generally owe their comparatively level 
surface to the absence of wrinkles or folds in the 
crust, in which case the general level is preserved, 
but the surface rises and falls in long undulations: 
these may therefore be called undulating plains. 

The flat surface may also be due to the gradual 
settling of sedimentary matter. In this case the 
plains are exceedingly level. They are called 
marine when deposited at the bottom of a sea or 
ocean, and alluvial when deposited by the fresh 
water of a river or lake. Alluvial plains occur 
along the lower course of the river or near its 
mouth. 

Marine and alluvial plains, from their mode of forma- 
tion, are generally less elevated than undulating plains. 

105. Plateaus are generally found associated 
with the mountain-ranges of the continents. Their 
connection with the adjacent plains is either ab- 
rupt, as where the plateau of Anahuac joins the 
low plains on the Mexican Gulf; or gradual, as 
where the plains of the Mississippi Valley join 
the plateaus east of the Rocky Mountains. 

106. Mountains. — In a mountain-chain the 
crest or summit of the range separates into a num- 
ber of detached portions called peaks; below the 
peaks the entire range is united in a solid mass. 

The breaks in the ridge, when extensive, form 
mountain-passes. 

The influence of inaccessible mountains, like the Pyr- 
enees and Himalayas, in preventing the intermingling of 
nations living on their opposite sides, is well exemplified 
by history. In the past, mountains formed the boundaries 
of different races. Some mountains, like the Alps and the 
Appalachians, have numerous passes. 

A Mountain-System is a name given to several 
connected chains or ranges. Mountain-systems 
are often thousands of miles in length and hun- 
dreds of miles in breadth. 

The Axis of a Mountain-system is a line extend- 
ing in the general trend of its chains. 

Where several mountain-axes intersect one an- 
other, a complicated form occurs, called a Moun- 
tain-Knot. 

The Pamir Knot, formed by the intersection of the 
Karakorum, Belor, and Hindoo-Koosh Mountains, is an 
example. It lies on the southern border of the elevated 
plateau of Pamir. 



44 



PHYSICAL GEOGRAPHY. 




Fig. 40. A Mountain-Pass. 

107. Orology treats of mountains and their 
formation. 

The force which upheaved the crust into moun- 
tain-masses and plateaus had its origin in the 
contraction of a cooling globe. There are good 
reasons for believing that no extensive mountains 
existed during the earlier geological ages, since 
the crust was then very thin, and would have 
been fractured before sufficient force could accu- 
mulate to upheave it into mountain-masses. 

The great mountain-systems of the world are 
formed from sedimentary deposits that slowly ac- 
cumulated over extended areas until they acquired 
very great thickness. The deposits forming the 
Appalachians, according to Dana, were, in places, 
40,000 feet in depth, and covered the eastern bor- 
der of the continent from New York to Alabama, 
varying from 100 to 200 miles in breadth. 

After the accumulation of these strata they 
were, through the contraction of the crust, sub- 
jected to the gradual effects of lateral pressure, 
by which they were sometimes merely flexed or 
folded, but more frequently crushed, fractured, or 
mashed together, and thus thickened and thrust 
upward. That side of the deposit from which 
the thrust came would have a steeper slope than 
the opposite side, which received a thrust arising 
from the resistance. 



This theory of mountain-formation, which is 
generally accepted, explains the following facts: 

(1.) All mountains have two slopes — a short 
steep slope, facing the ocean, and a long gentle 
slope, facing the interior of the continent. 

(2.) The strata on the short steep slope are 
generally highly metamorphosed ; those on the 
long slope are in general only partially metamor- 
phosed, or wholly unchanged. 

(3.) The mountain-systems are situated on the 
borders of the continents where the sedimentary 
strata collected. 

(4.) Slaty cleavage, or the readiness with which 
so many of the rocks of mountains cleave or split 
in one direction, is a proof of these rocks having 
been subjected to intense, long-acting, lateral pres- 
sure, since such pressure can be made to develop 
slaty cleavage in plastic material. 

Isolated Mountains. — Nearly all high isolated moun- 
tains were formed by the ejection of igneous rocks from 
the interior ; that is, they are of volcanic origin and have 
been upheaved by a vertical strain or true projectile force, 
as in the volcanic range of Jorullo in Mexico. 

108. Valleys in mountainous regions are either 
longitudinal or transverse. 

Longitudinal Valleys are those that extend in 
the direction of the length of the mountains. 

Transverse Valleys extend across the moun- 
tain. It is in transverse valleys that most passes 
occur. 

Although valleys, like mountains, owe their origin to 
the contraction of a cooling crust, yet their present shapes 
are modified by the operation of other forces. By the 
action of their water-courses, valleys are deepened in one 
place and filled up in another. Extensive land-slides often 
alter their configuration. Duriugthe Glacial Period many 
valleys were greatly changed by the action of huge mov- 
ing masses of ice. Fiord-valleys were formed in this 
manner. 

In level countries valleys generally owe their 
origin to the eroding power of water. 

109. Peculiarities of Continental Reliefs. — 
The following peculiarities are noticeable in the 
relief forms of the continents : 

(1.) The continents have, in general, high bor- 
ders and a low interior. 

(2.) The highest border lies nearest the deep- 
est ocean; hence, the culminating point, or the 
highest point of land, lies out of the centre of the 
continent. 

(3.) The greatest prolongation of a continent 
is always that of its predominant mountain-sys- 
tem. 

(4.) The prevailing trends of the mountain- 






RELIEF FORMS OF THE CONTINENTS. 



45 



masses are the same as those of the coast lines, and 
are, in general, either north-east or north-west. 

In describing the relief forms of the continents 
we shall observe the following order : 

(1.) The Predominant System, or a system of 



elevations exceeding all others in height, and con- 
taining the culminating point of the continent. 

(2.) The Secondary System or Systems, inferior 
to the preceding in height. 

(3.) The Great Low Plains. 




Pig, 41. Orographic Chart of North America, (Light portions, mountains ; shaded portions, plains.) 
3, Rocky Mountain System; 2, System of tbe Sierra Nevada and Cascade Ranges; 3, Sierra Madre; 4, Great Interior Plateau; 5, Wahsatch 
Mountains; G, Appalachians; 7, Plateau of Labrador; 8, Height of Land; 9, Arctic Plateau; 10, Mackenzie River; 11, Nelson River; 12, St. 
Lawrence River; 13, Mississippi River. 



CHAPTER V. 

Relief Forms of the Continents. 
I. NORTH AMERICA 

110. Surface Structure. — The Predominant 
Mountain-System lies in the west. 

The Secondary Systems lie in the east and north. 
The Great Low Plains lie in the centre. 

111. The Pacific Mountain-System, the pre- 
dominant system, extends, in the direction of the 
greatest prolongation of the continent, from the 
Isthmus of Panama to the Arctic Ocean. It con- 
sists of an immense plateau, from 300 to 600 
miles in breadth, crossed by two nearly parallel 
mountain-systems : the Rocky Mountains on the 
east and the system of the Sierra Nevada and 
Cascade ranges on the west. The eastern moun- 
tain-system is highest near the south ; the west- 
ern range is highest near the north. Between 
these lie numerous parallel ranges enclosing lon- 



gitudinal valleys, connected in places by trans- 
verse ranges forming basin-shaped valleys. 

The Rocky Mountain System. — The Rocky 
Mountains rise from the summits of a plateau 
whose elevation, in the widest part of the system, 
varies from 6000 to 7000 feet above the sea; 
therefore, although the highest peaks range from 
11,000 to nearly 15,000 feet, their elevation above 
the general level of the plateau is comparatively 
inconsiderable. The plateau on the east rises by 
almost imperceptible slopes from the Mississippi 
River. The upper parts of the slopes, near the 
base of the mountains, form an elevated plateau 
called the " Plains," over which, at one time, 
roamed vast herds of buffalo or bison. This ani- 
mal is rapidly becoming extinct. 

Though the name " Eocky Mountains " is generally con- 
fined to those parts of the chain which extend through 
British America and the United States, yet, in connection 
with the Sierra Nevada Mountains, it is continued through 
Mexico by the Sierra Madre Mountains, and by smaller 
ranges to the Isthmus of Panama. 



46 



PHYSICAL GEO.GRAPHY. 




jw4'7" 



Pig. 42. On the Plains. 



The Rocky Mountain System forms the great 
watershed of the continent, the eastern slopes 
draining mainly through the Mississippi into the 
Atlantic, and the western slopes draining through 
the Columbia and the Colorado into the Pacific. 
It slopes gradually upward from the Arctic Ocean 
toward the Mexican plateau, where it attains its 
greatest elevation in the volcanic peak of Popo- 
catepetl, 17,720 feet above the sea. 

The System of the Sierra Nevada and Cascade 
Mountains extends, in general, parallel to the 
Rocky Mountain System. It takes the name of 
Sierra Nevada in California and Nevada, and of 
the Cascade Mountains in the remaining portions 
of the continent. It reaches its greatest eleva- 
tion in Mount St. Elias, in Alaska, 19,500 feet 
above the sea. This is the culminating point of 
the North American continent. 

In the broadest part of the plateau of the Pacific system, 
between the Wahsatch Mountains on the east, and the 
Sierra Nevada and Cascade ranges on the west, lies the 
plateau of the Great Basin. Its high mountain borders 
rob the winds of their moisture, and the rainfall, except 
on the mountain-slopes, is inconsiderable. The Great 
Basin has a true inland drainage. 

The heights of all mountains, except those much fre- 
quented, must generally be regarded as but good approxi- 
mations, since the methods employed for estimating heights 
require great precautions to secure trustworthy results. 
Even the culminating points of all the continents have 
not, as yet, been accurately ascertained. 

112. The Secondary Mountain-Systems of North 
America comprise the Appalachian system, the 



Plateau of Labrador, the Height of Land, and 
the Arctic Plateau. The last three have but an 
inconsiderable elevation. 

The Appalachian Mountain System consists of 
a number of nearly parallel chains extending 
from the St. Lawrence to Alabama and Georgia. 
It is high at the northern and southern ends, and 
slopes gradually toward the middle. The highest 
peaks at either end have an elevation of about 
6000 feet. 

The Appalachian system is broken by two deep depres- 
sions, traversed by the Hudson and Mohawk Eivers. Be- 
tween the foot of the system and the ocean lies a low coast 
plain, whose width varies from 50 to 250 miles. 

113. The Great Low Plain of North America 
lies between the Atlantic system on the east and 
the Pacific system on the west. It stretches from 
the Arctic Ocean to the Gulf of Mexico. 

Near the middle of the plain the inconsider- 
able elevation of the Height of Land divides it 
into two gentle slopes, which descend toward the 
Arctic Ocean and the Gulf of Mexico. A gen- 
tle swell extending from north-west to south-east 
divides the northern portion of the plain into 
two parts. The eastern and western basins, so 
formed, are connected by a break in the water- 
shed, through which the Nelson River empties 
into Hudson Bay. 

The southern part of the plain is traversed, in 
its lowest parts, by the Mississippi River. 

The tributaries of this river descend the long, gentle 
slopes of the Atlantic and Pacific systems. 

114. The Relief Forms of a Continent are best 
understood by ideal sections, in which the base 
line represents the sea-level, and the scale of 
heights on the margin represents the elevation 
of the various parts. 

In all such sections the vertical dimensions of the land 
are necessarily greatly exaggerated. 



18.000 

12.000 

6000 

3000 




JJU 


I 5 







Fig. 43. Section of North America from East to West 
1, St. Elias; 2, Sierra Nevada; 3, Rocky Mountains; 4, Mississippi 
Valley ; 5, Appalachian System. 

115. Approximate Dimensions of North America. 

Area of continent, 8,400,000 square miles. 

Greatest breadth from east to west, about 3100 miles. 

Greatest length from north to south, about 4500 miles. 

Coast line, 22,800 miles. 

Culminating point, Mount St. Elias, 19,500 feet. 



RELIEF FORMS OF THE CONTINENTS. 



47 




Fig, 44, Orographic Chart of South America. 

(Light portions, mountains ; shaded portions, plains.) 

1, System of the Andes; 2, Plateau of Quito; 3, Plateau of Bolivia; 

4, Aconcagua; 5, Plateau of Guiana; 6, Plateau of Brazil; 7, The 

Orinoco ; S, The Amazon ; 9, The La Platte. 

II. SOUTH AMERICA. 

116. Surface Structure. — The Predominant 
Mountain-System of South America is in the west. 

The Secondary Systems are in the east. 
The Great Low Plain lies between them. 

117. The System of the Andes, which extends 
along the western border of the continent, is the 
predominant mountain-system. It is composed 
mainly of two approximately parallel chains 
separated by wide and comparatively level val- 
leys. On the north there are three chains, and 
on the south but one ; in the centre, mainly two. 
The chains are connected by transverse ridges, 
forming numerous mountain-knots. 

The Andes System forms a continuation of 
the Pacific Mountain-System. A wide depression 
at the Isthmus of Panama marks their separation. 
From this point the Andes increase in height 
toward the south, probably reaching their high- 
est point in Chili, where the volcanic peak of 
Aconcagua, 23,910 feet, is believed to be the cul- 
minating point of South America, and of the West- 
ern Continent. 

Nevada de Sorata was formerly believed to be the cul- 
minating point of South America, but recent recalculations 



of the observations have resulted in a loss of nearly 4000 
feet of the supposed height of Sorata. Some authorities 
still claim that several peaks in Bolivia reach an ele- 
vation of nearly 25,000 feet. 

The Andes Mountain-System terminates ab- 
ruptly in the precipitous elevations of Cape Horn. 

Numerous table-lands are included between the parallel 
ranges : the most important are — the plateau of Quito, 9543 
feet; the plateau of Pasco, in North Peru, 11,000 feet; the 
plateau of Bolivia, from 12,000 to 14,000 feet. From most 
of these higher plateaus volcanic peaks arise. 

118. The Secondary Mountain-Systems of South 
America are the plateaus of Brazil and Guiana. 
They both lie on the eastern border. 

The Plateau of Brazil is a table-land whose 
average height is about 2500 feet. Narrow 
chains or ridges separate the river-valleys. 

The plateau of Brazil forms the watershed between the 
tributaries of the Amazon and the La Plata. Along the 
Atlantic a moderately continuous range descends in steep 
terraces to the ocean. The average altitude is more than 
double that of the western portion of the plateau. The 
highest peaks are somewhat over 8000 feet. 

The Plateau of Guiana, smaller than the Plateau 
of Brazil, but about equally elevated, forms the 
watershed between the Orinoco and the Amazon. 




- r '~\" 



Fig, 45. Amazon Kiver Scenery. 

119. The Great Low Plain of South America 
lies between the predominant and the secondary 
mountain-systems. It is mainly of alluvial origin, 
but slightly elevated, and is much more level than 
the great plain of North America. 

This plain is drained by the three principal river-sys- 



48 



PHYSICAL GEOGRAPHY. 



tems of the continent, by which it is divided into three 
parts : the Llanos of the Orinoco, the Selvas of the Amazon, 
and the Pampas of the La Platte. 

The Llanos are grassy plains which, during the rainy 
season, resemble our prairies, but during the dry weather 
are deserts. 

The Selvas, or forest plains, are covered by an uninter- 
rupted luxuriant forest. The vegetation here is so dense 
that in some places the broad rivers form the only ready 
means of crossing the country. Near the river-banks are 
vast stretches of swampy ground. 

The Pampas are grassy plains which in some respects 
resemble the Llanos. 

A coast plain lies between the Andes and the 
Pacific. It is widest near the Andes of Chili, 




Section of South America from East to West. 

3, Nevada de Sorata; 4, 



Fig, 46, 
1, Volcano Arequipa; 2, Lake Titicaca 
Central Plain ; 5, Mountains of Brazil. 



where in some places it is 100 miles in breadth. 
Between the parallels of 27° and -23° the plain 



is an absolute desert, called the Desert of Ata- 
cama. Here rain never falls and vegetation is 
entirely absent. 

120. Approximate Dimensions of South America. 

Area of continent, about 6,500,000 square miles. 

Greatest breadth from east to west, 3230 miles. 

Greatest length from north to south, 4800 miles. 

Coast line, 14,500 miles. 

Culminating point, Aconcagua, 23,910 feet. 

121. Contrasts of the Americas. — In both North 
and South America the predominant system lies in 
the west, the secondary systems in the east, and the 
low plains in the centre. 

They differ in the following respects : 

In North America the predominant system is a 
broad plateau, having high mountain-ranges ; the 
principal secondary system is narrow, and formed 
of parallel ranges ; the low plains are character- 
ized by undulations, and contain several deep de- 
pressions occupied by extensive lake-systems. 

In South America the predominant system is nar- 
row; the secondary systems are broad; the low plain 
is alluvial, extremely flat, contains no depressions, 
and consequently no extensive lake-systems. 




Fig, 47, Orographic Chart of Europe. (Light portions, mountains ; shaded portions, plains.) 
1, The Alps; 2, Mont Blanc; 3, Pyrenees; 4, Cantabrian; 5, Sierra Estrella; 6, Sierra Nevada; 7, Mountains of Castile; 8, Apennines; 
9, Dinaric Alps; 10, Balkan; 11, Pindus; 12, Taurus; 13, Caucasus; 14, Cevennes; 15, Plateau of Auvergne; 16, Vosges; 17, Black Forest; 18, 
Jura; 19, Hartz; 20, Bohemian Plateau; 21, Carpathians; 22, Hungarian Forest; 23, Transylvanian Mountains; 24, Kiolen Mountains; 25, Urals. 



III. EUROPE. 
122. Surface Structure. — The Predominant 
Mountain-System is in the south. 

The Secondary Systems are in the north and east. 



The Great Low Plain lies between the Pre- 
dominant and Secondary Systems. 

A line drawn from the Sea of Azov to the mouth of the 
Rhine Eiver divides Europe into two distinct physical 



RELIEF FORMS OF THE CONTINENTS. 



49 



regions. The great low plain lies on the north, and the 
predominant mountain-system on the south. The coun- 
try north of this line is sometimes called Low Europe, and 
that south of it, Sigh Europe. 

123. The Predominant Mountain-System of Eu- 
rope is composed of a highly complex series of 
mountain-systems extending along the northern 
shores of the Mediterranean in a curve, from the 
Straits of Gibraltar to the shores of Asia Minor. 
The system is highest in the centre, where the 
Alps form the culminating point of the continent. 

The average elevation of the Alps ranges from 
10,000 to 12,000 feet. The highest peak, Mont 
Blanc, 15,787 feet, is the culminating point of the 
European continent. Matterhom and Monte Rosa 
are but little inferior in height. On the south- 
west the system is continued to the Atlantic by 
the Cevennes and adjoining ranges in France, and 
the Pyrenees and Cantabrian in the northern part 
of the Spanish peninsula. The Pyrenees are an 
elevated range, with peaks over 11,000 feet high. 
On the east the system extends in two curves to 
the Black Sea by the Carpathian and Transylva- 
nian Mountains on the north, and the Dinaric 
Alps and the Balkan Mountains on the south. 

124. Divisions of Predominant System. — The 
predominant mountain-system of Europe may be 
conveniently regarded as consisting of a central 
body or axis, the Alps, with six projections or 
limbs — three on the north, and three on the south. 

The three divisions on the north include — 

The Western Division, or the mountains of 
France, including the mountains lying west of 
the valleys of the Rhine and the Rhone ; 

The Central Division, or the mountains of Ger- 
many, situated between the Western Division and 
the upper valleys of the Oder and the Danube ; 

The Eastern Division, or the mountains of 
Austria-Hungary, situated between the Central 
Division and the Black Sea. 

These divisions contain a highly complicated system of 
minor elevations. Their complexity is due to the fre- 
quent intersection of the north-eastern and north-western 
trends. Basin-shaped plateaus, like the Bohemian and 
Transylvanian, are thus formed. 

The "Western Division includes most of the mountains 
of France, as the Cevennes, the mountains of Auvergne, 
and the Vosges Mountains. 

The Central Division includes the Jura Mountains in 
Switzerland, the Swiss and the Bavarian plateaus, the 
Black Forest Mountains, the Hartz Mountains, and the 
Bohemian plateau. 

The Eastern Division includes most of the mountains 
of Austria, as the Carpathians, the Hungarian Forest, and 
the Transylvanian Mountains. 

125. The three projections on the south are the 



three mountainous peninsulas of Southern Eu- 
rope: 

The Iberian Peninsula, including Spain and 
Portugal ; 

The Italian Peninsula ; 

The Turco-Greeian Peninsula. 

The Iberian Peninsula.— The principal mountains are 
the Sierra Estrella, the mountains of Castile, and the 
Sierra Nevada. The Pyrenees separate the Peninsula from 
France. The Cantahrian Mountains extend along the 
northern coast. 

The Italian Peninsula contains the Apennines, ex- 
tending mainly in the direction of the north-western 
trend. 

The Turco-Grecian Peninsula.— The Dinaric Alps 
extend along the coast of the Adriatic ; the Balkan Moun- 
tains extend from east to west, through Turkey ; and the 
Pindus from north to south, through Turkey and Greece. 

126. The Secondary Mountain-Systems of Eu- 
rope comprise the system of the Scandinavian 
peninsula, the Ural Mountains, and the Cauca- 
sus Mountains. 

The System of the Scandinavian Peninsula 
includes the elevations of Norway and Sweden. 
With the exception of the Kiolen Mountains in 
the north, the system does not embrace distinct 
mountain-ridges, but consists mainly of a series 





Pig. 48, Fiord on Norway Coast, 

of broad plateaus that descend abruptly on the 
west in numerous deeply-cut valleys called fiords, 
through which the sea penetrates nearly to the 
heart of the plateaus. Fiords are valleys that 
were deeply eroded by slowly moving masses of 



50 



PHYSICAL GEOGRAPHY. 



ice, called glaciers, and subsequently partially sub- 
merged. On the east the slopes are more gradual, 
and are occupied by numerous small lakes. 

The System of the "Urals is composed of a 
moderately elevated range extending from the 
Arctic Ocean on the north to the plains of the 
Caspian on the south. The elevated island of 
Nova Zembla may be considered as forming a 
part of its northern prolongation. 

The Caucasus Mountains bear peaks exceeding 
in elevation those of the Alps. They belong, 
however, more properly to the elevations of 
Asia. 

127. The Great Low Plain of Europe lies be- 
tween the predominant and secondary mountain- 



systems, and stretches north-eastwardly from the 
Atlantic to the Arctic. It is remarkably level, 
and is highest in the middle, where the Valdai 
Hills form the principal watershed of Europe. 
Westward the plain is continued under the North 
Sea to the British Isles, where a few inconsider- 
able elevations occur. 

South of the Alps the large plain of the Po 
River stretches across the northern part of Italy. 

128. Approximate Dimensions of Europe. 
Area of continent, 3,700,000 square miles. 
Coast line, 19,500 miles. 

Greatest breadth from north to south, 2400 miles. 
Greatest length from north-east to south-west, 3370 
miles. 

Culminating point, Mont Blanc, 15,787 feet. 




Fig. 49, Orographic Chart of Asia, (Light portions, mountains ; shaded portions, plains.) 
1, Himalaya Mountains; 2, Karakorum; 3, Kuen-lun; 4, Belor; 5, Thian Shan; 6, Altai; 7, Great Kinghan; 8, Tablonoi; 9, Nanling; 
lO.Pellng; 11, Vindhya; 12, Ghauts; 13, Hindoo-Koosh ; 14, Elburz; 15, Suliman ; 16, Zagros; 17, Taurus; 18, Caucasus; 19, Asiatic Island Chain. 



IV. ASIA. 

129. Surface Structure. — The Predominant 
Mountain-System is in the south. 

The Secondary Systems surround the Predomi- 
nant System. 

The Great Low Plain is on the north and west, 



and lies between the mountain-systems of Asia 
and the secondary system of the Urals. 

Europe and Asia are sometimes considered as geographic- 
ally united in one grand division called Eurasia. 

130. The mountain-systems of Asia are nearly 
all connected in one huge mass which extends in 



RELIEF FORMS OF THE CONTINENTS. 



51 



the line of the north-east trend, from the Arctic to 
the Indian Ocean. Though in reality one vast 
system, yet they are most conveniently arranged 
in one predominant and several secondary systems. 
The Predominant System is the plateau of 
Thibet, the loftiest table-land in the world. It 
is between 15,000 and 16,000 feet high, and is 
crossed by three huge, nearly parallel, mountain- 
ranges : the Himalayas on the south, the Kuen- 
lun on the north, and the Karakorum between 
them. The Himalayas, the loftiest mountains 




Fig. 50. Himalaya Mountains. 

in the world, rise abruptly from the plains of 
Northern Hindostan. Like the Alps, their axis 
is curved, but in the opposite direction. The 
breadth of the system varies from 100 to 200 
miles ; the length is about 1500 miles. The high- 
est point is Mount Everest, 29,000 feet above the 
sea ; it is the culminating point of the Asiatic con- 
tinent and of the world. Kunchinjunga and Dha- 
walaghiri are scarcely inferior in height. 

131. The Secondary Systems lie on all sides of 
the predominant system, though mainly on the 
north and east of the predominant system. Like 
Europe, the Asiatic continent projects on the 
south in the three mountainous peninsulas of 
Arabia, Hindostan, and Indo-China. 

On the north and east of the plateau of Thibet 
is an extended region called the plateau of Gobi, 
considerably lower than the surrounding country. 
The Kuen-lun and Great Kinghan Mountains 
bound it on the south and east, and the Altai 
7 



Mountains on the north. On the west lie the 
Thian Shan and Altai, which by their open val- 
leys afford ready communication with the low 
plains on the west. 

The plateau of Gobi varies in average height from 2000 
to 4000 feet. The greatest depression is in the west, and 
is occupied by Lake Lop and the Tarim Eiver. A small 
part of the region near the mountain-slopes is moderately 
fertile, the remainder is mainly desert. 

The Altai Mountains are but little known, but some of 
their peaks exceed 12,000 feet. They are continued east- 
ward by the Yablonoi Mountains. East of the plateau of 
Gobi a range extends north-easterly through Mantchooria. 

On the south and west of Thibet lie the pla- 
teaus of Iran, Armenia, and Asia Minor. 

The Plateau of Iran includes Persia, Afghan- 
istan, and Beloochistan. It is a basin-shaped 
region from 3000 to 5000 feet high. The Elburz 
and Hindoo-Koosh Mountains form its borders on 
the north, the Suliman on the east, and the Za- 
gros on the south and west. 

The Suliman Mountains rise abruptly from the plains 
of the Indus. Across these mountains occurs the only 
practicable inland route between Western Asia and the 
Indies. 

The Plateaus of Armenia and of Asia Minor 

lie west of the Plateau of Iran. Armenia is 8000 
feet high, and bears elevated mountains : Mount 
Ararat, 16,900 feet, is an example. On the west, 
the vjeninsula of Asia Minor, or Anatolia, extends 
between the Black and Mediterranean Seas, and 
is traversed by the Taurus Mountains. 

The Caucasus Mountains lie north of the pla- 
teau of Armenia. They are an elevated range 
extending between the Black and Caspian Seas, 
and form part of the boundary-line between Eu- 
rope and Asia. Mount Elburz, the " Watch- 
Tower," the culminating peak, is 18,493 feet 
high. 

The Arabian Plateau occupies the entire penin- 
sula of Arabia. It is separated from the plateau 
of Iran by the Persian Gulf and the valleys of 
the Tigris and the Euphrates. 

The Plateau of Deccan occupies the lower part 
of the pieninsula of Hindostan. It is crossed on 
the north by the Vindhya Mountains, and along 
the coasts by the Eastern and Western Ghauts. 

The Peninsula of Indo-China is traversed by 
a number of mountain-ranges which diverge from 
the eastern extremity of the Himalayas. The 
Nanling and Peling extend from east to west 
through China. 

132. The Great Low Plain is, in reality, but a 
continuation of the European plain. It extends 
from the Arctic Ocean south-westerly to the Cas- 



52 



PHYSICAL GEOGRAPHY. 



pian and Black Seas. It is hilly on the east, but 
level on the west. South of the 60th parallel it 
is comparatively fertile. Around the shores of 
the Arctic are the gloomy Tundras. 

The Tundras are vast regions which in summer are 
covered with occasional moss-beds, huge shallow lakes, 
and almost interminable swamps, and in winter with thick 
ice. The tundras are caused as follows : The rivers that 
flow over the immense plain of Asia rise in the warmer 
regions on the south. Their upper courses thawing while 
the lower courses are still ice-bound, permits large quan- 
tities of drift ice to accumulate at their mouths, which, 
damming up the water, causes it to overflow the adjoining 
country. 

Depressions of the Caspian and Sea of Aral. — 

Two remarkable depressions occur in the basins 
of the Caspian and Sea of Aral, and that of the 
Dead Sea. These are all considerably below the 
level of the ocean. The waters of the Caspian 
and Sea of Aral were probably once connected 
in a great inland sea. 



The Smaller Asiatic Plains are drained by 
several river-systems. These are the Plain of 
Mantchooria, drained by the Amoor ; the Plain 
of China, drained by the Hoaug-Ho and the 
Yang-tse-Kiang ; the Plain of India, drained by 
the Indus, the Ganges, the Brahmapootra, and 
the Irrawaddy ; and the Plain of Persia, drained 
by the Tigris and the Euphrates. 

133. Approximate Dimensions of Asia. 

Area of continent, 17,500,000 miles. 

Coast line, 35,000 miles. 

Greatest length from north-east to south-west, 7500 miles. 

Greatest breadth from north to south, 5166 miles. 

Culminating point, Mount Everest, 29,000 feet. 

134. Comparison of the Relief Forms of Eu- 
rope and Asia. — In both Europe and Asia the 
chief elevations are in the south and the great low 
plains in the north. Asia, like Europe, extends 
toward the south in three great peninsulas : Ara- 
bia, Hindostan, and Indo-China. 




Fig. 61. Section of Asia from North to South, 
1, Cape Comorin ; 2, Deccan ; 3, Plain of India ; 4, Himalayas ; 5, Everest ; 6, Kuen-lun ; 7, Karakorum ; 8, Thibet ; 9, Upper Tartary ; 10, 
Ararat ; 11, Elburz ; 12, Thian Shan ; 13, Altai ; 14, Mountains of Kamtchatka ; 15, Arctic Ocean , mouth of Yenesei. 




Fig, 52, Orographio Chart of Afrioa. 
(Light portions represent mountains ; shaded portions, plains.) 
1, Abyssinian Plateau; 2, 3, Kenia and Kilimanjaro ; 4, Lupata; 
5, Dragon; 6, Nieuveldt; 7, Mocambe; 8, Crystal; 9, Cameroons; 10, 
Kong; 11, Atlas; 12, Lake Tchad; 13, Madagascar. 



V. AFRICA. 

135. Surface Structure. — Nearly the entire con- 
tinent of Africa is a moderately elevated plateau. 
It therefore has no great low plains ; but the in- 
terior is lower than the marginal mountain-sys- 
tems, and in this respect the true continental type, 
high borders and a low interior, is preserved. 

136. The Predominant Mountain-System is in 
the east. 

The Secondary Systems are in the south, west, 
and north. 

The great interior depression is in the middle, 
and is surrounded by the predominant and sec- 
ondary systems. 

A narrow, low plain extends along most of the 
coast. It is broadest on the north-west, between 
the plateau of the Sahara and the Atlas Moun- 
tain-system. 

137. The Predominant Mountain-System ex- 
tends along the entire eastern shore, from the 
Mediterranean Sea to the southern extremity of 
the continent. It is highest near the centre, in 



RELIEF FORMS OF THE CONTINENTS. 



53 



the plateaus of Abyssinia and Kaffa. The culmi- 
nating point is probably to be found in the vol- 
canic peaks of Kenia and Kilimandjaro, whose 
estimated heights are taken at about 19,000 feet. 
In the Abyssinian plateau, on the north, an aver- 
age elevation of from 6000 to 8000 feet occurs. 
Upon this, rising in detached groups, are peaks 
the highest of which are over 15,000 feet. 

From the Abyssinian plateau the system is con- 
tinued northward to the Mediterranean by a suc- 
cession of mountains which stretch along the 
western shores of the Red Sea. Some of the 
peaks are from 6000 to 9000 feet. South of the 
plateau of Kaffa the system is continued by the 
Lupata and Dragon Mountains to the southern 
extremity of the continent. The Zambesi and 
Limpopo Rivers discharge their waters into the 
Indian Ocean through deep breaks in the system. 

138. Secondary Systems. — On the south the 
Nieuveldt and Snow Mountains stretch from east 
to west, with peaks of over 10,000 feet. Table 
Mountain is on the south. 




Pig. 53. Table Mountain, 

On the west the Mocambe and Crystal Mountains 
extend from the extreme south to the Gulf of 
Guinea. Near the northern end of this range, 
but separate from it, are the volcanic peaks of 
the Cameroons Mountains, 13,000 feet high. 

The Kong Mountains extend along the north- 
ern shores of the Gulf of Guinea in a general 
east-and-west direction. Some of the peaks are 
snow-capped. In the extreme north of Africa 
are the Atlas Mountains, which rise from the 
summit of a moderately elevated plateau. Some 
of the peaks are 13,000 feet high. 

139. The Great Interior Depression north of 
the equator is divided into two distinct regions. 
A straight line extending from Cape Guardafui 
to the northern shores of the Gulf of Guinea 
marks the boundary. The mountain-systems 



north of this line have a general east-and-west 
direction ; those south of it have a general north- 
and-south direction. 

The Plateau of the Sahara occupies the north- 
ern part of the interior depression. Its general 
elevation is about 1500 feet, though here and 
there plateaus of from 4000 to 5000 feet occur, 
and even short mountain-ranges with peaks of 
6000 feet. The main portion of the region is cov- 
ered with vast sand-fields, with occasional rocky 
masses, and is one of the most absolute deserts 
in the world. 




Fig, 54, Desert of Sahara. 

Near long. 14° E. from Greenwich, in the district of 
Fezzan, the plateau is divided from north to south by a 
broad valley. In this occur many remarkable depressions, 
some of which are several hundred feet below the level of 
the Mediterranean. Here fertile spots, called oases, are 
common. 

South of the Sahara is the Soudan, a remark- 
ably well-watered and fertile region. Lake Tchad 
occupies the greatest depression. The interior, 
which lies south of this, is but little known. It 
is probably a moderately elevated plateau. Ex- 
tensive lake-basins — Albert and Victoria Nyan- 
zas and Tanganyika — lie near the predominant 
mountain-system. 

140. Approximate Dimensions of Africa. 
Area of continent, 12,000,000 square miles. 
Coast line, 16,000 miles. 

Greatest breadth from east to west, 4800 miles. 
Greatest length from north to south, 5000 miles. 
Culminating point, Mount Kenia, or Kilimandjaro, 
about 19,000 feet. 



54 



PHYSICAL GEOGRAPHY. 




Fig. 56. Orographic Chart of Australia. 
(White portions, mountains ; shaded portions, plains.) 
1, Auetraliau Alps; 2, Kosciusko; 3, 4, 5, Secoudary Systems; 6, 
Murray River. 

VI. AUSTRALIA. 

141. Surface Structure. — The Predominant 

Mountain-System is in the east. 

The Secondary Systems are in the west and 
north-west. 

The Great Low Plain lies between the pre- 
dominant and secondary systems, and slopes 
gently to the southern coast. 

The Predominant System extends along the 
entire eastern shore, from Torres Straits to the 
southern extremity of Tasmania. It is for the 
most part composed of broad plateaus. The 
system is highest in the south-east, where the 
name Australian Alps is given to the range. 
Mount Kosciusko, 7000 feet, probably forms the 
culminating point of the Australian continent. 

The system descends abruptly on the east, but 
on the west it descends by gentle slopes to the 
low plains of the interior. 

142. The Secondary Systems, on the west and 
north-west, are of but moderate elevation. 

143. The Great Low Plain lies in the interior. Ac- 
curate information as to its peculiarities is yet wanting. 
A moderate elevation on the north connects the eastern 
and western systems. The south-eastern portion, which 
is the best known, is well watered and remarkably fertile. 
Basin-shaped valleys are found in the west. The lower 
parts are occupied by Lake Eyre, Torrens, and Gairdner. 



144. Approximate Dimensions of Australia. 
Area of continent, 3,000,000 square miles. 
Coast line, 10,000 miles. 

Greatest length from east to west, 2400 miles. 
Greatest breadth from north to south, 2000 miles. 
Culminating point, Mount Kosciusko, 7000 feet. 

145. Contrasts of Africa and Australia. — In 
the north, the African continent resembles Europe 
and Asia in the arrangement of its forms of 
relief. In the south, it resembles the Americas. 
As a whole, the African continent resembles 
Australia more closely than any other. In both 




Fig. 56. Australian Scenery. 

Africa and Australia the predominant system is 
in the east, and extends along the entire coast. 
In each the secondary systems are in the west 
and north. But Africa terminates in a plateau 
which descends abruptly to the sea, while Australia 
is terminated by a great low plain which descends 
by long, gentle slopes from the interior. 



— *~ir~Gzg_^$z3Zz~s~3 — 



SYLLABUS. 



►oXKo 



Eock-masses are divided, according to their origin, into 
igneous, aqueous, and metamorphic. According to their con- 
dition, into stratified and unstratified. According to the 
presence or absence of organic remains, into fossiliferous 
and non-fossiliferous. Stratified rocks are sometimes called 



fragmeutal. Unstratified rocks are sometimes called crys- 
talline. Aqueous rocks are sometimes called sedimentary. 

Aqueous rocks are stratified. Igneous rocks are un- 
stratified. Metamorphic rocks were originally stratified, 
but lost their stratification through metamorphism. 



REVIEW QUESTIONS. 



55 



Aqueous rocks may contain fossils. Igneous rocks never 
contain fossils. Metainorphic rocks, in rare instances, may 
contain fragments of fossils. 

Geological time is divided into Archxan, Palseosoic, Meso- 
zoic, and Cenozoic. 

Archaean Time includes the Azoic and the Eozoic Ages. 

Palaeozoic Time, or, as it is sometimes called, the Pri- 
mary, includes the Silurian, Devonian, and Carboniferous 
Ages. 

Mesozoic Time, or the Secondary, includes the Age of 
Reptiles. 

Cenozoic Time includes the Age of Mammals, or the Ter- 
tiary, and the Era of Man, or the Quaternary Age. 

The changes to which the earth's crust is now subject 
are produced by the following agencies: 

1. By the winds ; 2. By the moisture of the atmosphere; 
3. By the action of running water; 4. By the action of 
ocean waves ; 5. By the agency of man ; 6. By the con- 
traction of a cooling crust. 

There is more water than land surface on the earth, in 
proportion of 25 : 9, or as 5 5 : 3\ 

The land-masses surround the north pole in the shape 
of an irregular ring. 

Nearly all the land-areas are collected in one hemi- 
sphere, and the water-areas in another. 

The Land Hemisphere comprises the whole of North 
America, Europe, and Africa, all of Asia except a small 
part of the Malay Peninsula, and the greater part of South 
America. 

The Water Hemisphere comprises the whole of Australia 
and the southern portions of South America and the Ma- 
lay Peninsula. 

The northern continents are almost entirely in the tem- 
perate latitudes ; the southern are mainly in the tropics. 

The land-masses may be divided into three doublets, 
consisting of pairs of northern and southern continents, 
almost or entirely separated from each other. 

There are two great systems of trends or lines of direc- 
tion, along which the continents, the coast lines, the 
mountain-ranges, the oceanic basins, and the island chains 
are arranged. These trends are north-east and north-west. 

The northern continents are characterized by deeply in- 
dented coast lines ; the southern are comparatively simple 
and unbroken. Europe is the most, and Africa the least, 
deeply indented of the continents. 

In proportion to her area, Europe has three times as 
much coast line as Asia, and four times as much as Africa. 

One-seventeenth of the land-area is composed of islands. 

Islands are either continental or oceanic. 

There are four successive stages in the formation of a 
coral island or atoll: 1. The fringing reef; 2. The barrier 
reef; 3. The encircling reef; 4. The coral island or atoll. 

The greatest elevations and depressions in the earth's 
surface are small when compared with its size. 



Low lands are either plains or hills. 

High lands are either plateaus or mountains. 

Plains are— 1. Undulating; 2. Marine; 3. Alluvial. 

Mountains were produced by the contraction of the 
crust, producing a lateral pressure on thick, extended de- 
posits of sedimentary rocks. Slaty cleavage was caused 
by this lateral pressure. 

Valleys are either longitudinal or transverse. 

All continents have high borders and a low interior. 
The highest border faces the deepest ocean. 

The greatest prolongation of a continent is that of its 
predominant mountain-system. The culminating point is 
always out of the centre. 

North and South America resemble each other in the 
arrangement of their relief forms. Their predominant 
systems are in the west; their secondary systems are in 
the east ; their great low plains are between the predomi- 
nant and secondary systems. 

The predominant system of North America is the Pa- 
cific mountain-system. The secondary systems are— the 
Appalachian system, the plateau of Labrador, the Height 
of Land, and the Arctic plateau. 

The predominant system of South America is the sys- 
tem of the Andes. The secondary systems are — the pla- 
teaus of Guiana and Brazil. The great low plains are — 
the Llanos of the Orinoco, the Selvas of the Amazon, and 
the Pampas of the La Plata. 

Europe and Asia resemble each other. Their predomi- 
nant systems are in the south ; their great low plains are 
north of their predominant systems. The predominant 
system of Europe is in the south. 

The secondary systems are — the mountains of the Scan- 
dinavian Peninsula, the Ural Mountains, and the Caucasus 
Mountains. 

The predominant mountain-system of Asia is the pla- 
teau of Thibet. 

The secondary systems are — the plateau of Gobi, the 
Thian-Shan and Altai Mountains, the plateau of Indo- 
China, the plateau of Deccan, the plateau of Iran, the pla- 
teau of Asia Minor, and the plateau of Arabia. 

Africa and Australia resemble each other. Their pre- 
dominant systems are in the east; their secondary systems 
are in the west and north ; their depressed areas are be- 
tween the two. 

The predominant mountain-system of Africa includes 
the mountains of the eastern coast. 

The secondary systems include the Nieuveldt and Snow 
Mountains in the south, the Mocambe, Crystal, Cameroons, 
and Kong Mountains in the west, and the Atlas Mountains 
in the north. 

The predominant mountain-system of Australia includes 
the mountains of the eastern coast. 

The secondary systems include those found in the south, 
west, and north. 



REVIEW QUESTIONS. 



What two elementary substances form the greater part 
by weight of the earth's crust? 

Into what classes may rocks be divided according to 
their condition ? According to their origin ? According 
to the presence or absence of fossils? 

What is palaeontology? 



Define Archsean Time, Palaeozoic Time, Mesozoic Time, 
and Cenozoic Time. 

Explain the nature of the changes which the atmo- 
sphere is now effecting in the earth's surface. Which the 
water is effecting. Which man is effecting. 

What must be the areas of two squares whose areas 



56 



PHYSICAL GEOGEAPHY. 



represent the relative land- and water-areas of the earth ? 
What are the actual areas in square miles? 

How would you draw a circle around the earth which 
will divide it into land and water hemispheres? 

Do the continents extend farther to the north pole or to 
the south pole ? 

What do you understand by lines of trend ? 

Which have the more diversified coast lines, the north- 
ern or the southern continents ? 

Define continental and oceanic islands, and give exam- 
ples of each. Why are continental islands to be regarded 
as detached portions of the neighboring mainland? 

Name the American island chains. The Asiatic chains. 

Describe the Australasian island chain. The Polynesian 
chain. 

Which are the higher, volcanic islands or coral islands ? 
Why? 

Name the four principal steps or stages in the progress 
of formation of a coral island. 

Is the coral island built by the coral animalcule or by 
the waves? Explain your answer. 

What is Darwin's theory for the presence of a lagoon 
within the reef? 

What is the difference between a plain and a plateau? 
A mountain and a hill? 

Define mountain-system. A chain. A knot. 

What is the name of the highest plateau in the world? 
Of the largest plain ? 

In what different ways were plains formed ? 

Distinguish between a longitudinal and a transverse 
valley. Explain the manner in which mountains were 
formed. 

Give a short account of the surface structure, or the 
arrangement of the high and low lands, of North America. 
Of South America. Of Europe. Of Asia. Of Africa, and 
of Australia. Which of these resemble each other? In 
what respect do they all resemble one another? 

Name the culminating points of each of the continents. 

Name the predominant and secondary mountain-systems 
of each of the continents. 

How many times larger is Asia than Australia? Than 
Europe? Africa? North America ? South America? 

North America. 
Name the principal mountains of the Pacific mountain- 
system. Which contains the culminating point of the 
continent? 



Where is the Great Basin ? By what mountains is it 
surrounded ? 

Name the principal mountains of the Appalachian sys- 
tem. 

Is the greater portion of the area of North America 
above or below 1000 feet? 

What rivers drain the great low plain of North Amer- 
ica? 

South America, 

Name the principal plateaus of the Andes. Through 
which does the equator pass? Which contains Lake Titi- 
caca? 

Where is the plateau of Guiana? Of Brazil? 

What three large river-systems drain the great low plain 
of South America ? What resemblances can you find be- 
tween the directions of these rivers and those which drain 
North America ? 

Europe. 

Describe the chain of the Alps. 

What river-systems divide its northern slope into three 
divisions ? Name the principal mountains of each division. 

What three peninsulas project southward from the south- 
ern slopes of the predominant mountain-system? 

Name the principal mountains of each peninsula. 

Name the great low plains of Europe. 

Asia. 

What mountains form the northern boundary of the 
plateau of Thibet? The southern boundary? The north- 
ern boundary of the plateau of Mongolia? The eastern 
boundary? What mountains extend through China? 

What mountains form the boundaries of the plateau of 
Iran ? Is Arabia a plateau or a plain ? 

Is the land north of the Sea of Aral high or low? 

In which line of trend do the mountainous elevations 

of Asia extend? 

Africa. 

What portions of Africa are high ? What portions are 
low? 

Where is the predominant system? Where is the cul- 
minating point? What part of the interior is low ? 

Where are the Mocambe Mountains ? The Crystal Moun- 
tains, the Cameroons, the Atlas, the Kong, the Lupata, and 

the Dragon ? 

Australia. 

Where is the predominant mountain-system? The sec- 
ondary system ? 
Where is Mount Kosciusko ? The Murray Kiver ? 





Part III 



THE WATER. 




m*. . 




sUB 







By contact of air with the water-areas, an immense quantity of invisible vapor passes into the 
atmosphere, from which, when sufficiently cooled, it re-appears and descends as fog, dew, rain, hail, sleet, 
or snow. It then, in greater part, drains through various lake- and river-systems into the ocean, where 
it is either again evaporated, or carried about in waves, tides, or currents. This circulation of water 
never ceases, and upon it depends the existence of all life on the earth. 



Section I. 



CONTINENTAL WATERS. 



0»«0 



CHAPTER I. 

Physical Properties of Water. 

146. Composition. — Water is formed by the 
combination of oxygen and hydrogen, in the pro- 
portion, by weight, of eight parts of oxygen to 
one part of hydrogen ; or, by volume, of one part 
of oxygen to two parts of hydrogen. 

147. Properties. — Pure water is a colorless, 
transparent, tasteless, and inodorous liquid. It 



freezes at 32° Fahr., and, under the ordinary 
pressure of the atmosphere, boils at 212° Fahr. 

Water exists in three states : solid, liquid, and gaseous. 
Under ordinary circumstances it freezes at 32°. It evapo- 
rates, or passes off from the surface as vapor, at all tempera- 
tures, even at 32° ; but it is only at the boiling-point that 
the vapor escapes from the mass of the liquid as well as 
from the surface. 

Heated in open vessels, under the ordinary pressure of 
the atmosphere, its temperature cannot be raised higher than 
212°, any increase of heat only causing it to boil more rap- 
idly. Heated in closed vessels, which prevent the escape 

57 



58 



PHYSICAL GEOGRAPHY. 



of steam, its temperature can be raised very high. In 
such cases great pressure is exerted on the walls of the 
vessel. Conversely, on high mountains, where the pres- 
sure of the atmosphere is lower than at the level of the 
sea, water boils at temperatures lower than 212° Fahr. 

148. Maximum Density of Water. — A pint of 
cold water is heavier than a pint of warm water, 
because as water is cooled it contracts and grows 
denser. The coldest pint of water, however, is 
not the heaviest. The heaviest pint of water is 
water at the temperature of 39.2° Fahr. This 
temperature is therefore called the temperature 
of the maximum density of water. If water at 
this temperature be heated, it becomes lighter, or 
expands ; if water at this temperature be cooled, 
it also becomes lighter or expands until ice is 
formed, which floats on the water. When at the 
temperature of its maximum density, water is 
7.2° warmer than the freezing-point. 

149. Effect of the Maximum Density of Water 
on its Freezing. — If water continued to contract 
indefinitely while cooling until freezing began, 
the ice first formed would sink to the bottom, and, 
this process continuing, the entire mass would soon 
become solid. In this manner all bodies of fresh 
water, in times of great cold, might freeze through- 
out ; when, not even the heat of a tropical sun 
could entirely melt them. 

But, for this curious exception in the physical properties 
of water, at least three-fourths of the globe would be in- 
capable of sustaining its present life. 

The entire floor of the ocean, both in the tropics and in 
the temperate and the polar regions, is covered with a layer 
of cold, salt water at nearly the temperature of its maxi- 
mum density. In the tropics the surface-water is warmer 
and lighter than this dense layer, and in the polar re- 
gions it is colder and lighter. 

150. Specific Heat of Water. — Another re- 
markable property of water — its specific heat — 
enables it to play an important part in the 
economy of the world. 

The specific heat of a body is the quantity of 
heat-energy required to produce a definite in- 
crease of temperature in a given weight of that 
body. 

Water has a very great specific heat ; that, is, 
a given quantity of water requires more heat-energy 
to warm it, and gives out more heat-energy on cool- 
ing, than an equal quantity of any other common 
substance. 

The quantity of heat required to raise a pound of ice- 
cold water to 212°, would heat a pound of ice-cold iron to a 
bright red heat, or to about 1600° Fahr. ; or, conversely, a 
pound of boiling water cooling to the freezing-point, would 
give out as much heat as a pound of red-hot iron cooling 
to 32° Fahr. 



The enormous capacity of water for heat is of 
great value to the life of the earth. The oceanic 
waters are vast reservoirs of heat, storing heat in 
summer and giving it out in winter. The great 
specific heat of water prevents it from either heat- 
ing or cooling rapidly. Large bodies of water, 
therefore, prevent great extremes of heat and 
cold. 

151. Heat Absorbed or Emitted during Change* 
of State. — During the conversion of a solid into 
a liquid, or a liquid into a vapor, a large quantity 
of heat-energy is absorbed. This heat-energy does 
not increase the temperature of the body, and 
therefore cannot be detected by the thermometer. 
The heat-energy is then in the condition of stored 
or potential energy, sometimes called latent heat. 
When the vapor condenses into a liquid, or the 
liquid freezes, the stored heat-energy again becomes 
sensible as heat. 

In freezing, water gives out heat and raises the 
mean temperature of the atmosphere. 

In melting, ice takes in heat and loivers the mean 
temperature of the atmosphere. 

Water has a higher latent heat than any other 
common substance. 

Stored Heat-Energy of Ice- Cold Water. — In 
order to heat a pound of water 1° Fahr. an 
amount of heat called a heat-unit, or a pound 
degree is required. Before one pound of ice at 
32° Fahr. can melt and form one pound of water 
at 32° Fahr., it must take in 1J$ heat units ; and 
yet a thermometer plunged in the water from 
melting ice will indicate the same temperature as 
when entirely surrounded by lumps of the un- 
melted material. 

The great latent heat of ice-cold water has an important 
influence on the freezing of large bodies of water, since, 
after the surface-layers have reached the temperature of 
the freezing-point, they have still 142 heat-units to lose be- 
fore they can solidify. Again, when ice reaches a tempera- 
ture of 32° Fahr., it has still 142 heat-units to absorb before 
it can melt. Were it not for this fact destructive floods 
would often result from the rapid melting of the winter's 
accumulation of snow and ice. 

Stored Seat-Energy of Water- Vapor. — Before 
one pound of water can pass off as vapor, it 
must take in sufficient heat to raise nearly 1000 
pounds of water 1° Fahr. The vapor which then 
escapes is still at the same temperature as the 
water from which it came. The 1000 heat-units, 
or pound-degrees of heat, have been rendered latent, 
and have no influence on the thermometer. 

When the vapor in the air is condensed as rain, 
snow, hail, fog, or cloud . the stored heat-energy 



DRAINAGE. 



59 



again becomes sensible. Much of the vapor 
which is formed in the equatorial regions is car- 
ried by the winds to high northern latitudes, 
where, on condensing, it gives out its heat and 
moderates the intense cold which would otherwise 
exist. 

152. Solvent Powers. — Water is one of the best 
solvents of all common substances. During the 
constant washings to which the continents are 
subjected by the rains, their surfaces are cleansed 
from decaying animal and vegetable matters, 
which are partly dissolved and carried by the 
rivers into the ocean. The atmospheric waters 
in the same way cleanse the air of many of its 
impurities. 

153. Water is the Main Food of Animals and 
Plants. — -By far the greater part of the bodies of 
animals and plants is composed of water. With- 
out large quantities of water no vigorous life can 
be sustained in any locality. 

Deserts are caused entirely by the absence of 
water. 



CHAPTER II. 

Drainage. 

154. Drainage. — The atmospheric waters, or 
those which fall from the atmosphere as rain, 
hail, or snow, either sink through the porous 
strata and are drained under ground, or run 
directly off the surface. Thus result two kinds 
of drainage — Subterranean and Surface. 

155. Subterranean Drainage. — The water which 
sinks through the porous strata continues descend- 
ing until it meets impervious layers, when it either 
runs along their surface, bursting out as springs 
at some lower level, where the layers outcrop, or 
it collects in subterranean reservoirs. The origin 
of all springs is to be traced to subterranean 
drainage. 

Underground streams sometimes attain considerable size. 
In portions of the Swiss Jura streams burst from the sides 
of hills in sufficient volume to turn the wheels of moder- 
ately large mills. In a few instances the subterranean 
stream can be navigated for considerable distances, as in 
the Mammoth Cave of Kentucky, or in the Grotto of 
Adelsberg, near Trieste. 

156. Surface Drainage. — The water which is 
drained directly from the surface, either runs 
down the slopes in rivulets and rills, which, 
uniting with larger streams, are poured directly 
into the ocean, or it collects in the depressions of 



basin-shaped valleys, where, having no connection 
with the ocean, it can be discharged by evapora- 
tion only. Thus arise two kinds of surface drain- 
age — oceanic and inland. 

157. Springs are the outpourings of subterra- 
nean waters. The waters, having soaked through 
the porous strata, again emerge at the surface, 
either — 

(1.) By running along an inclined, impervious 
layer of clay, hard rock, or other material until 




Fig, 57. Origin of Springs, 

they emerge at some lower level, where the strata 
outcrop ; or, 

(2.) By being forced upward out of the reser- 
voirs into which they have collected by the pres- 
sure of compressed gas, highly heated steam, or, 
more commonly, by the pressure of a communi- 
cating column of water. 

It is in the first way that most of the springs of moun- 
tainous districts discharge their waters. The tilted and 
broken condition of the strata is such as to favor the es- 
cape along some of the many layers that crop out on the 
mountain-slopes. The springs of plains, which are at some 
distance from mountains, discharge their waters mainly by 
the methods mentioned under the second heading. 

When a well is dug in most porous soils, the water from 
the porous strata on the sides runs in and partially fills 
the opening. 

158. Classification of Springs. — Springs are 
most conveniently arranged in different classes 
according to peculiarities in the size, shape, and 
depth of their reservoirs, and the nature of the 
mineral substances composing the strata over which 
the waters flow, or in which they collect. 

The Reservoirs of springs are the places where 



60 



PHYSICAL GEOGRAPHY. 



the waters that sink into the ground collect. 
Reservoirs are sometimes large subterranean 
basins, but more frequently are merely porous 
strata, such as beds of sand or gravel, which lie 
between impervious layers of clay or hard rock. 
The water collects in the spaces between the par- 
ticles of sand or gravel. 

159. Size of Reservoir. — When the reservoir 
is large, the spring is constant; when small, the 
spring is temporary. 

Constant Springs are those which flow continu- 
ally, and are but little affected in the volume of 
their discharge even by long-continued droughts. 

Temporary Springs are those which flow only 
for a short time after wet weather, drying up on 
the appearance of even moderate droughts. 

The quantity of water discharged by a spring depends on the 
size of the orifice or outlet tube, and the depth of the outlet be- 
low the surface of the water in the reservoir. The flow is 
proportional to the square root of the depth. That is to 
say, if with a given depth of orifice the velocity he one 
foo* per second, in order to make the water escape with 
twice the velocity the depth must be increased fourfold. 
The actual velocity is somewhat less than this, being di- 
minished by friction. 

Since the volume discharged by some springs 
is very considerable, we must infer that their 
reservoirs are of great size. Many springs prob- 
ably receive the drainage from hundreds of 
square miles of surface. 

ISO. Shape of the Reservoir. — When the out- 
let tube of the reservoir is siphon-shaped, the dis- 
charge of the spring becomes periodical. The 




Fig. 58. A Periodical Spring. 

spring continues to discharge its waters for a 
time, and then stops flowing, even during wet 
weather. After a certain interval it again dis- 



charges. The times during which the spring con- 
tinues to discharge are always practically the 
same. Hence the spring is called a periodical 
srjring. 

The cause of periodical springs is due to the siphon- 
shape of the outlet tube. A siphon is a tube so bent as to 
have two vertical arms of unequal length. When filled, 
it will continue to discharge as long as its shorter arm is 
below the water and the longer arm free. If a large cav- 
ernous reservoir be in connection with the surface of the 
earth by a tube of this shape, it will begin to discharge its 
water when, by infiltration, the level reaches the highest 
bend of the tube, as at a, in Fig. 58, since the water will then 
drive out the air and fill the entire tube. The discharge 
will then continue until the water-level falls below the 
mouth of the tube, or at b, in the figure. The time of the 
discharge is always practically the same, since the same 
quantity is discharged each time under exactly similar 
conditions. 

Springs are common on the shores of the ocean. Their 
waters are fresh because the outflow of the fresh water 
prevents the inflow of the salt water. This is the case 
even on coral islands, where the height of the laud is 
but ten or twelve feet above the sea. A comparatively 
shallow well, on such islands, generally yields fresh water, 
derived, of course, from the rainfall. 

161. Depth of Reservoir. — According to the 
distance the reservoir is situated below the sur- 
face of the earth, springs are divided into Cold, 
and Sot or Thermal. 

Cold Springs are those whose temperature does 
not exceed 60° Fahr. Their waters are sometimes 
much colder than 60° Fahr. 

Very cold springs owe their low temperatures 
to the sources whence they draw their supplies. 
In mountainous districts these can generally be 
traced to the melting of huge snow-fields, or 
masses of ice called glaciers. The temperature 
in such cases is often nearly that of ordinary ice- 
water. 

The reservoirs of all springs the temperature 
of whose waters ranges from 50° to 60° are, in 
general, comparatively near the surface. They 
are colder than surface waters — 

(1.) Because they are shielded from the sun ; 

(2.) Because evaporation occurs in their cav- 
ernous reservoirs. 

The temperature of springs of this kind is, in 
general, but slightly affected by changes in the 
temperature of the outer air. Since the reservoirs 
of ordinary springs are shielded from the hot air 
in summer and from the cold air in winter, their 
waters are colder than river-water in summer, and 
warmer than river-water in winter. Their waters 
average, in their temperature, that of the strata 
over which they flow in their subterranean course. 



DRAINAGE. 



61 



The mean annual temperature of the strata over 
which the waters flow can, therefore, he ascertained 
■ by plunging a thermometer into the water as it 
comes out of the spring. 

Hot or Thermal Springs range in temperature 
from 60° Fahr. to the boiling-point. In geysers 
the temperature of the water far down in the tube 
is considerably above the boiling-point at the sur- 
face. 

Hot springs which occur in the neighborhood 
of active volcanoes owe their high temperature to 
the vicinity of their reservoirs to beds of recently- 
ejected lava. 

Hot springs, however, are common in regions 
distant from volcanic disturbance. In such cases 
their high temperature must be attributed to the dis- 
tance of their reservoirs from the earth's surface, the 
heat being derived directly from the interior. 

In some cases the source of the heat is to be attributed 
to chemical action in neighboring strata. 

Thermal springs, whose reservoirs are at comparatively 
moderate depths, may discharge their waters by ordinary 
hydrostatic pressure ; but where, from the great depth of 
the reservoirs, this force would be insufficient, the waters 
are probably raised to the surface by the pressure of super- 
heated steam or compressed gas. 

Since the temperature rises 1° for about every 55 feet of 
descent, in cases where the increased temperature is due 
solely to depth, if the issuing waters have a tempera- 
ture of 149° Fahr., the reservoirs must be about one mile 
below the surface, or fifty-five times the difference between 
149° and 60°, the temperature of ordinary springs. In 
many cases the waters probably rise from profound depths 
as columns of steam, condensing in reservoirs that are less 
profound. 

Source of Deep-seated Waters. — Deep-seated waters 
are probably derived by infiltration from the bed of the 
ocean. The natural porosity of large areas is greatly in- 
creased by the immense pressure of the water, which in 
the deep ocean is equal to thousands of pounds per square 
inch. 




Fig. 59. Artesian Well. 

162. Artesian Wells differ from ordinary wells 
in that their waters are discharged by natural 



pressure on their reservoirs, so that pumping is 
not necessary to raise the water. Such wells are 
therefore true springs. 

The reservoirs are basin-shaped, and generally 
consist of several water-logged, porous strata, con- 
tained between two, curved, impervious strata. If 
the upper porous layer be pierced, the waters will 
flow out by reason of the pressure of the liquid 
in the higher parts. The reservoirs of many 
natural springs are of this kind, the upper im- 
pervious strata being broken in one or more 
places by some natural force. 

Artesian wells have been sunk to great depths, and it is 
a significant fact that the temperature of the issuing 
waters is always proportional to the depth, showing a 
nearly constant increase of 1° above the temperature of 
ordinary springs — viz. about 60° Fahr. — for every 55 feet 
of descent. In the case of the artesian well of Grenelle, 
Paris, the successful boring of which was accomplished 
only after many years of the most discouraging labor, 
and which reached a depth of nearly 1800 feet, the tem- 
perature of the water was 82° Fahr. A well at Neusalz- 
werk, Prussia, has penetrated 2200 feet; its temperature 
is 91° Fahr. 

163. Geysers are boiling springs which, at in- 
tervals more or less regular, shoot out huge col- 
umns of water with great violence. They are 




Fig. 60, Geyser in Eruption. 

confined to the neighborhood of volcanic dis- 
tricts, and, by some, are classed with subordinate 
volcanic phenomena. The jets of water some- 



62 



PHYSICAL GEOGRATHY. 



times reach a height of more than two hundred 
feet. 

The geyser issues from the summit of a conical hillock 
of silicious material deposited by the water. A broad, 
shallow basin generally surmounts the hillock and forms 
the mouth of a deep, funnel-shaped tube. The sides of 
both tube and basin are lined with a smooth incrustation 
of silica. In the Great Geyser of Iceland, the basin is 52 
feet wide and the tube 75 feet deep. 

Both the tube and basin are the work of the spring, 
being deposited from the silica contained in the highly 
heated waters. It is only when the tube has reached a 
certain depth that the spring becomes a true geyser. 
When the depth becomes too great the geyser eruptions 
cease, the waters forcing their way through the walls of 
the tube to some lower level. Hence, in all geyser re- 
gions, numerous deserted geyser-tubes, and simple ther- 
mal springs occur. 

The waters of some geyser regions are calcareous. In 
this case the tube of the geyser is, of course, formed of 
limestone. 

164. Bunsen's Theory of Geysers. — Bunsen explains 
the cause of geyser eruptions as follows : The heat of the 
volcanic strata, through which the geyser-tube extends, 
causes the water which fills it to become highly heated. 
The water at the bottom of the tube, having to sustain 
the pressure of that above it, gradually acquires a tem- 
perature far above the boiling-point at the surface. The 
temperature of the water in the tube will, therefore, de- 
crease from the bottom to the surface. 

If now, when the tube is filled, the water, near the mid- 
dle, is brought to its boiling temperature, the steam thus 
formed momentarily lifts the water in the upper part of 
the tube, when the water in the lower part, released from 
its pressure, bursts into steam and forcibly ejects the con- 
tents of the tube. 

Bunsen succeeded in lowering a thermometer into the 
tube of the Great Geyser in Iceland just before an erup- 
tion. At the depth of 72 feet he found the temperature 
of the water to be 261° Fahr., or 49° above the ordinary 
boiling-point. 

165. Geyser Regions. — There are three exten- 
sive geyser regions : 

(1.) In Iceland, in the south-western part of 
the island, where over one hundred occur in a 
limited area. 

(2.) In New Zealand, about the centre of the 
northern island, where, near the active volcano 
Tongariro, over one thousand mud springs, hot 
springs, and geysers burst from the ground. 

(3.) In Yellowstone National Park, in Wyoming, 
where numerous large geysers occur, mostly near 
the head-waters of the Madison and Yellowstone 
Rivers, at heights often as great as 8000 feet 
above the sea-level. Here the boiling-point of 
the water at the surface of the geyser, owing to 
the diminished atmospheric pressure, is as low 
as about 200° Fahr. 

A small geyser region is found in California, 
near San Francisco. 



166. Nature of the Mineral Substances form- 
ing the Reservoir. — The subterranean waters dis- 
solve various mineral matters either from the 
strata over which they flow, or from their reser- 
voirs ; this is especially true of thermal springs, 
owing to the greater solvent powers of the heated 
waters. 

The waters of mineral springs generally contain 
a number of mineral ingredients. Mineral springs 
are divided into various classes according to the 
predominating material. 

(1.) Calcareous Springs are those whose waters 
contain lime in solution. 

Thermal waters charged with carbonic acid usually con- 
tain large quantities of lime, which they have dissolved 
from subterranean strata. On reaching the surface the 
waters cool and part with some of their carbonic acid, and 
deposit layer after layer of hard limestone, called travertine. 
In this way immense quantities of limestone are brought 
to the surface from great depths, leaving huge subterra- 
nean caverns. 

In portions of Tuscany, Italy, beds of travertine occur 
more than 250 feet thick. 

(2.) Silicious Springs are those whose waters 
contain silicon. 

(3.) Sulphurous Waters are those whose waters 
contain sulphuretted hydrogen and various metal- 
lic sulphides or sulphates. 

Sulphurous springs are found in Baden, near Vienna, 
and in Virginia. 

(4.) Chalybeate Springs are those whose waters 
contain iron. 

(5.) Salt Springs or Brines are those whose 
waters contain common salt. 

The springs of Halle, in the Alps of Salzburg, yield 
15,000 tons of salt aunually. The artesian well of Neu- 
salzwerk, Prussia, yields about 28,000 tons annually. In 
the United States the springs of Salina and Syracuse are 
among the most important. The water in the springs of 
Salina is ten times Salter than ocean-water. The salt is 
obtained from these springs by the evaporation of the 
water. 

(6.) Acidulous Springs are those whose waters 
contain large quantities of carbonic acid gas, as 
the Seltzer springs in Germany, and those of 
Vichy in France. 

167. Petroleum and Bituminous Springs. — Be- 
sides the springs above mentioned, there are two 
others, closely connected, but which can scarcely 
be included in any of the above classes. These 
are petroleum and bituminous springs. 

Petroleum Spring's are those containing rock- or coal- 
oil. They rise from large reservoirs containing oil instead 
of water. The oil is derived from the slow decomposition, 
in the presence of heat, of various animal and vegetable 



RIVERS. 



63 



matters which are found in the strata of nearly all the 
geological formations. The reservoirs are of the same 
nature as those of artesian wells, the oil being obtained 
by boring. 

Petroleum springs are numerous. The most extensive 
regions in the world are found in the great oil districts of 
Western Pennsylvania and the neighboring States. 

Bituminous Springs, or those from which pitch or 
bitumen issue. Their origin is the same as that of oil 
springs, the decomposition, however, occurring in a some- 
what different way. The famous pitch lake on the island 
of Trinidad, north-east of South America, probably owes 
its origin to the large quantities of trees and other vege- 
table matters, which have been rolled down the Orinoco 
and buried in the delta formation on the eastern shores 
of the island. 



oXKo 



CHAPTER III. 

Rivers. 

168. Definitions. — The water that issues from 
the ground as springs, that is derived from the 
melting of ice or snow, or that drains directly 
from the surface after rainfall, runs down the 
slopes of the land and collects in the depressions 
formed by the intersection of the slopes, forming 
rills or rivulets, which at last combine in larger 
streams called rivers. 

The source of a river is the place where it 
rises ; the mouth, the place where it empties ; the 
channel, the depression through which it flows. 
Rivers generally rise in mountains, where the 
rainfall is greater than elsewhere, and where 
vast beds of snow and ice occur. 

In reality, all rivers have three mouths, or places where 
they discharge their waters : 

(1.) Where the river empties directly into some other 
body of water; 

(2.) Where the river empties by evaporation into the 
air ; that is, its entire upper surface ; 

(3.) Where the river empties into the earth through the 
porous strata of its bed or channel. 

Since the downward motion of a river is caused by the 
inclination of its channel from the source to the mouth, a 
correct idea of the general inclination of any country can 
be obtained by a careful study of a map in which the di- 
rections of the rivers are represented. In studying the 
various river-systems the student should endeavor to ob- 
tain in this way clear ideas of the general directions of the 
continental slopes. 

The River-System is the main stream, with all 
its tributaries and branches. 

The Basin is the entire area of land which 
drains into the river-system. 

The Water-shed is the ridge or elevation which 



separates two opposite slopes. The streams flow 
in opposite directions from the water-shed. 

The Velocity of a river depends on the inclina- 
tion or pitch of the channel and the volume or 
depth of the water. 

169. River-Courses. — The river-channel, from 
its source to its mouth, is, for ease of description, 
conveniently divided into three parts or courses : 
the upper, middle, and lower. 

The Upper Course of a river is that part which 
is situated in the mountainous or hilly country 
near its source. In this course the river has a 
great velocity, and its channel is characterized by 
sharp, sudden turns, alternating with long, straight 
courses. In the upper course erosion occurs 
almost entirely along the bottom of the channel, 
so that the river runs between steep, and some- 
times almost vertical, banks. In this way river- 
valleys are formed, generally with narrow and 
overhanging, precipitous sides. In the upper and 
middle courses rapids and waterfalls occur. 

Rapids and Waterfalls. — During the erosion of 
the channel, where harder rocks occur in the bed 
of the stream, the softer strata, immediately adjoin- 
ing them down stream, are rapidly worn away, and 
the obstruction becomes at last the head of a 
waterfall. The height grows rapidly from the 
increased force of the falling water, and continues 
until stopped by some similar obstruction below. 



a 










a 






\ 


G \ 


5 


i ■ 




1 


sV_ 


o 




2 




3 

i 




3 






4 



Fig. 61. Erosion of Waterfall, 

Thus, suppose a a, Fig. 61, is the bed of a river, the di- 
rection of flow of which is shown by the arrow. The softer 
rock being worn away more rapidly, the bed reaches the 
level 1, 1. A fall, and consequent increase in the velocity 
of the river, soon causes the level of the bed to reach 2. 2, 
3, 3, and 4, 4, successively. At the same time the falling 
water eats away the vertical wall of the precipice, causing 
the waterfall to move up stream. The water then cuts the 
precipice away in steps, as shown at 5, 6, 7, thus changing 
the fall into cascades. These are finally worn away, as 
shown at 8, changing the cascades to rapids, when, finally, 
the fall disappears entirely, or the erosion of the hard 
rock is completed. 

When the water falls perpendicularly — that is, 
when it does not slip or slide — it forms a wafer- 
fall or cataract; in all other cases of swift de- 
scent it forms rapids. 



64 



PHYSICAL GEOGRAPHY. 




Fig, 62. The Falls of Niagara, 

The grandest falls in the world are those of the Niagara, 
160 feet high. Though greatly inferior to many others in 
height, yet their volume of water is so great that they 
surpass all others in grandeur. The Victoria Falls of the 
Zambezi in Africa nearly equal in volume those of the 
Niagara. Their height is 360 feet. 

The highest falls in the world are those of the Yosemite, 
in California. Two projecting ledges break the sheet into 
three falls, whose total height exceeds 2000 feet. One of 
the highest falls in Europe is the Staubbach or Dust-brook, 
in the valley of the Lauterbriinnen in Switzerland. The 
water makes one sheer fall of 959 feet, and is lost in a 
sheet of mist before it reaches the ground. 

The Middle Course extends from where the 
river emerges from the mountainous or hilly dis- 
tricts to the low plains near the mouth. The 
descent is comparatively slight, and the velocity 
small. The erosion of the bottom of the channel 
is insignificant, but at the sides, especially during 
freshets, the river undermines its banks and thus 
widens its valley. Here the river is divided into 
two distinct portions: the channel proper and the 
alluvial flats or flood-grounds. 

The Lower Course extends from the middle 
course to the mouth. The fall is slight, and the 
velocity small. 

170. Changes in River-courses. — During floods, when 
the velocity and eroding power are greatly increased, ex- 
tensive changes often occur in river-courses. After the 
floods have subsided the water is found running through 
new channels, its old ones being either completely filled 
with deposits of mud, or occupied by slender streams. 
Along the Mississippi these partially deserted channels 
are called bayous, and, in places, widen out into large lakes. 



(See Fig. 63.) The Eed River appears to have formerly 
emptied into the Mexican Gulf through a separate chan- 
nel. In the basins of the Amazon, the Ganges, and the 
Po, the old deserted channels are numerous on both banks 
of the streams. 

171. River Mouths. — A wide, open river-mouth 
is called an Estuary; the accumulation of mud 
or sand which occurs in the mouths of certain 
rivers is called a Delta. 

172. Inundations. — During certain seasons of 
the year, the amount of water drained into the 
river-channel is greater than it can discharge ; it 
then overflows its banks and inundates the sur- 
rounding country. 

Inundations of rivers are caused — 

(1.) By excessive rainfall ; 

(2.) By periodical rains ; 

(3.) By the melting of ice and snow. 

In the tropics, where the rainfall is more or 
less periodical, the inundations of the rivers are 
also periodical. The melting of the ice and snow, 
which occurs regularly at the beginning of the 
warm weather, also causes periodical inundations. 
The Nile rises annually on account of the period- 
ical rainfall of its upper sources ; the Mississippi 
semi-annually, once from the melting of snow, 
and once from the winter rainfall. 

When both the area of the river-basin and the rainfall 
in inches are known, experience permits of a calculation, 
by means of which the probable time and extent of rise of 
water in a river can be approximately predicted. In times 
of heavy rainfall, the Weather Bureau of the United 
States is enabled to predict the probable rise of the im- 
portant rivers. 

Influence of the Destruction of the Forests on In- 
undations. — When the forests are removed from a large 
portion of a river-basin, the rains are no longer absorbed 
quietly by the ground, but drain rapidly off its surface into 
the river-channels, and thus in a short time the entire 
precipitation is poured into the main channel, causing an 
overflow. It is from this cause that the disastrous effects 
of otherwise harmless storms are produced. The inunda- 
tions are most intensified by this cause in the early spring, 
when the ice and snow begin to melt. The destructive 
effects of the floods are increased by masses of floating ice, 
which, becoming gorged in shallow places in the stream, 
back up the waters above. The increased frequency of 
inundations in the United States is, to a great extent, to 
be attributed to the rapid destruction of the forests. 

173. The Quantity of Water Discharged by a 
River depends principally — 

(1.) On the size of the basin ; 
(2.) On the amount of the rainfall. 

The quantity of water in a river also depends — 
(1.) On the climate of the basin, a dry, hot air diminish- 
ing the quautity by evaporation ; 

(2.) On the physical features of the basin, whether wooded 
or open ; 



TRANSPORTING POWER OF RIVERS. 



65 



(3.) On the nature of the ted or channel, whether leaky 
or not. 

It will be noticed that these three circumstances are 
connected with the two additional river-mouths already 
alluded to : the air-surface of the river, and the channel- 
surface. 

Keith Johnston estimates the daily discharge of all the 
rivers of the world at 229,000,000,000 cubic yards, or over 
2,620,000 cubic yards per second. 



«>t*:o 



CHAPTER IV. 
Transporting Power of Rivers. 

174. Silt or Detritus. — Rivers are ceaselessly 
at work carrying the eroded materials, called silt 
or detritus, from their upper to their lower courses. 
Valleys are thus formed, miles in width and thou- 
sands of feet in depth, and lofty mountains greatly 
reduced in height. 

The amount of silt transported by rivers is almost in- 
credible. According to the careful estimates of Hum- 
phreys and Abbot, the silt brought down every year by 
the Mississippi and thrown into the Mexican Gulf, if 
collected in one place, would cover a field one square mile 
in area to the depth of 268 feet. According to Lyell, the 
deposits, in the Bay of Bengal, of the Ganges and the 
Brahmapootra, are nearly as great. 

The rivers are carrying/ the mountains seaivard, 
and the continents are thus decreasing in mean 
height and increasing in mean breadth. 

175. Deposition of Silt. — Since the silt or 
eroded mineral matter is heavier than water, it 
will settle in all parts of the river-course. It will, 
however, remain in those places only where the 
velocity of the river is comparatively small. 
These places are as follows: 

(1.) In the channel of the river ; 
(2.) On the banks, over the alluvial flats or 
flood-grounds ; 

(3.) At the mouth ; 
' (4.) Along the coast near the mouth. 

176. In the Channel. — In rivers that traverse 
great plains, the inclination near the mouth is 
slight, and the diminished velocity allows the ma- 
terial to accumulate in the channel, thus raising 
the general level of the stream. "When the rivers 
traverse settled districts, the inhabitants are com- 
pelled to erect huge river-walls to prevent the 
flooding of the adjacent lands ; and, in some places, 
the channel has been filled to such an extent that 
the ordinary level of the river is higher than that 
of the plains along its banks. 

The levees or banks of the Mississippi are of this nature. 
On the level plain of Lombardy the surface of the Po, in 



some places, is higher than the tops of the neighboring 
houses. When floods occur in such districts, the breaking 
of a levee or river-wall is generally attended by much 
loss. 

177. Rafts. — Drift timber, thrown into the stream by 
the undermining of the banks, is common in rivers that 
traverse wooded districts. Portions of such timber, be- 
coming imbedded in shallow parts of the channel, form 
obstructions which prevent the passage of subsequent 
masses. The impediment so formed checks the velocity 
of the stream, and mud deposits occur between the trees. 
Such accumulations are called rafts. The raft of the Bed 
Eiver, previous to its removal, was thirteen miles in length. 
A large raft exists near the mouth of the Mackenzie Eiver 
in British America. 

178. On the Alluvial Flats or Flood-grounds. 

— The low flat plains on the sides of the river, 
which are formed by the erosion of the banks in 
the middle and lower courses, are covered by the 
water when the river overflows its banks. In the 
shallow water over these parts the velocity of the 
water is slight, and the silt is deposited, thus 
forming rich alluvial plains. 

In large rivers the flood-grounds often attain consider- 
able size. In the Mississippi at Vicksburg the width of 
the alluvial plain is over 60 miles. 

In the lower courses of a river, the velocity 
being small, comparatively slight obstacles suffice 
to turn the waters from their course. The river- 
channel is therefore characterized by wide bends 




f. 


-«§. s 




n PS< 


t^ l/^%^\\ ' 


A 7^ 


Li: 


rsix^JX}-- 





Pig. 63. Alluvial Flats of the Mississippi, 
(Showing deserted courses and fluviatile islands and lakes.) 

or curves. At the bend of a river the main cur- 
rent is directed against one of the banks, where 
rapid erosion takes place, the eroded material ac- 



66 



PHYSICAL GEOGRAPHY. 



cumulating lower down the river, in the bed of 
the stream, where the velocity is small. The river 
is thus continually damming 
up portions of its old chan- 
nel and cutting new ones. 

The rapid excavation of 
these portions of the alluvial 
plain is favored by the loose 
materials which compose it. 
Sometimes the river cuts a 
new channel across the nar- 
row neck of a bend, part of 
its waters running through 
the old channel and part 
through the new. In this 
way fluviatile islands are 
formed. One of the chan- 
nels is sometimes separated 
from the other by a deposi- 
tion of mud or sand. The 
water fills the old channel 
by soaking through the soil, 
and thus fluviatile lakes are 
formed. Numerous fluviatile 
lakes occur near the banks of the Lower Missis- 
sippi and the Red River. 




Fig, 64. 
Fluviatile 
Lakes, 



Formation of 
Islands and 



Thus, suppose the river flows in the direction of the 
arrow at S, Fig. 64, and its channel has the bends shown. 
A new channel may he formed at a, 6, the river either 
flowing through both channels, thus converting the neck 
of land I, into a fluviatile island, or the old channel may- 
fill up and form a fluviatile lake, L, by bars forming in 
the old channel at a and b. 

179. At the Mouth. — Delta Formations. — In 

sheltered parts of the ocean, where the tides are 
weak and the ocean-currents feeble, or in inland 
seas and lakes, where they are entirely absent, the 
eroded material accumulates at the mouth of the 
river in large, triangular-shaped deposits, called 
deltas, from their resemblance to the Greek letter 
(J) of that name. 

The Delta of the Mississippi is the largest in the 
Western Continent. Its entire area is about 12,300 square 
miles, though but two-thirds of it are permanently above 
the water, the remainder being a sea-marsh. It begins a 
little below the mouth of the Red River. The stream cuts 
through the delta in one main channel, but near the ex- 
treme end of the delta forms several mouths. On all sides 
of the main stream, numerous smaller streams force their 
way into the Gulf through the soft material. 

The Delta of the Nile, at its outlet into the Mediter- 
ranean, occupies an area of nearly 9000 square miles. A 
large portion of the sediment of the river is deposited over 
the flood-grounds during inundations. The fertility of the 
land is largely dependent on these deposits. 




Fig. 65. Delta of the 



The Delta of the Ganges and the Brahmapootra, 
in the Bay of Bengal, is considerably larger than the Delta 
of the Nile. Between the Hoogly and the main branch 
of the Ganges, numerous streams force their way between 
countless islands, called the Sunderbunds, inhabited by 
tigers and crocodiles. The Po, the Rhone, the Rhine, and the 
Danube in Europe, the Tigris, the Euphrates, the Yang-tse- 
Kiang and Hoang-Ho in Asia, and the Senegal and the Zam- 
hesi in Africa, have extensive deltas. 



(After Dana.) 



180. Along the Coast, near the Mouth. — Fluvio- 
Marine Formations are deposits of silt that form 
along the coast near and opposite the mouths of 
rivers, under the combined action of the river- 
current and the tides of the ocean. A sand-bar 
is formed at some little distance from the mouth 
of the river, where the outflowing river-current 



DRAINAGE SYSTEMS. 



67 




Fig. 66. Fluvio- Marine Formations. 

and the inflowing tide neutralize each other. The 
impediment so formed permits of the rapid de- 
position of silt, which fills up the portions of the 
ocean so shut off, and converts them into shallow 
bodies of water called sounds. These sounds, by 
gradual rising of the land, are afterward con- 
verted into river-swamps. According to Dana, 
the eastern and southern coasts of the United 
States, from Virginia to Texas, are an almost con- 
tinuous fluvio-marine formation. Albemarle and 
Pamlico Sounds and the Great Dismal, Alligator, 
and Okefinoke Swamps are but different stages in 
the formation of these deposits. 



CHAPTER V. 

Drainage Systems. 

181. Continental Drainage is dependent on the 
position of the mountain-systems and the direc- 
tion of their slopes. The mountain-ridges or 
peaks, or the high plateaus, form the water-sheds. 
In some cases, from a single peak or plateau, the 
water drains into distinct river-systems, emptying 
into different oceans. 

182. North America. — The central plain of 
North America is drained by four large river- 
systems : the Mackenzie into the Arctic Ocean ; 
the Saskatchewan and the Nelson into Hudson 
Bay ; the St. Lawrence into the Gulf of St. Law- 



rence ; and the Mississippi into the Gulf of Mex- 
ico. The basin of the Mississippi occupies the 
long slopes of the Rocky Mountains and the 
Appalachians. The Missouri and the Ohio are 
the principal tributaries of the Mississippi. 

Numerous streams descend the eastern slopes 
of the Appalachian system into the Atlantic. 

Owing to the position of the predominant sys- 
tem, the streams which empty into the Pacific are 
comparatively small. The principal are the Yu- 
kon, the Columbia, and the Colorado. 

There are several remarkable isolated water-sheds or 
drainage-centres in North America. These are — 

(1.) In the central part of the Eocky Mountain system, 
where the land drains in different directions into the sys- 
tems of the Mississippi, the Columbia, and the Colorado 
Eivers. 

(2.) In the northern part of the Eocky Mountains, 
where the drainage is received by the systems of the 
Yukon, the Mackenzie, and the Saskatchewan Eivers. 

183. South. America resembles North America 
in its drainage systems. The long, gentle slopes 
of the Andes, and those of the systems of Brazil 
and of Guiana, are occupied at their intersections 
by the three great river-systems of the continent : 
that of the Orinoco, in the north ; that of the 
Amazon, near the centre; and that of the La 
Plata, in the south. Nearly the entire continent 
is drained by these rivers and their tributaries 
into the basin of the Atlantic. 

The Pacific receives no considerable streams. 
Only impetuous mountain-torrents are found. 

The Magdalena, which drains north, corresponds to the 
Mackenzie; the Orinoco and the Amazon, which drain 
east, to the Nelson and the St. Lawrence; aud the La 
Platte, which drains south, to the Mississippi. 

184. Europe forms an exception to the other 
continents as regards its drainage. Though some 
of its large rivers rise in its predominant moun- 
tain-system, yet the majority rise in the incon- 
siderable elevations of the Valdai Hills. The 
Alps are drained by four large rivers — the Rhone, 
the Rhine, the Danube, and the Po. These all 
have large deltas. 

Although in this part of the continent the frequent in- 
tersection of the two lines of trend produces numerous 
basin -shaped valleys, yet, owing to breaks in the enclosing 
mountains, none of any size have an inland drainage, but 
discharge their waters through numerous tributaries into 
one or another of the principal river-systems. 

The Great Low Plain of Europe is drained 
toward the north and west by the Petchora and 
Dwina into the Arctic ; by the Duna, the Nie- 
men, the Vistula, and the Oder into the Baltic ; 



Page. 68. 




LAKES. 



69 



and by the Elbe and the Weser into the North 
Sea. It is drained toward the south and east by 
the Ural and the Volga into the inland basin of 
the Caspian ; and by the Don, the Dnieper, and 
the Dniester into the Sea of Azov and the Black 
Sea. 

All the peninsulas have streams traversing them. The 
Seine, the Loire, and the Garonne from France, and the 
Douro, the Tagus, and the Gaudiana from Spain and Por- 
tugal, empty into the Atlantic. The Ebro from Spain, 
and the Po from Italy, empty into the Mediterranean. 

185. Asia possesses the most extensive inland 
drainage of all the continents. The plateaus are 
surrounded by lofty mountains containing but 
comparatively few breaks, and their waters, there- 
fore, can find no passage to the sea. The outer 
slopes, however, are drained by some of the 
largest rivers in the world. 

The Great Northern Plain drains into the 
Arctic, mainly through the Lena, the Yenisei, 
and the Obe. 

The Eastern Slopes drain into the Pacific 
through the Amoor, the Hoang-Ho, the Yang-tse- 
Kiang, and the Cambodia. 

The Southern Slopes drain into the Indian 
Ocean through the Irrawaddy, the Brahmapootra, 
the Ganges, the Indus, the Tigris, and the Eu- 
phrates. 

The principal drainage-centre in Asia is the Plateau of 
Thibet, from which descend the Hoang-Ho, the Yang-tse- 
Kiang, the Cambodia, the Irrawaddy, the Ganges, the 
Brahmapootra, and the Indus. 

186. Africa, being low in the interior, with 
high mountain-walls on her borders, is charac- 
terized, like the Americas, by the union of her 
smaller river-systems into a few large streams, 
which drain nearly the entire continent. These 
embrace the Nile, emptying into the Mediterra- 
nean ; the Zambezi, into the Indian Ocean ; and 
the Orange, the Congo, the Niger, and the Senegal, 
into the Atlantic. 

187. Australia. — The Murray, which drains the 
south-eastern part of the continent into the Indian 
Ocean, is the only considerable stream. 

188. Principal Oceanic Systems. — A careful 
study of the river-basins of the different oceans 
discloses the following fact: 

The Atlantic and Arctic Oceans receive the 
waters of nearly all the large river-systems of the 
world. 

The cause of this is as follows : The predomi- 
nant systems being situated nearest the deepest 
ocean, the long, gentle slopes descend toward the 
9 



smaller, shallower oceans (the Atlantic and the 
Arctic), which thus receive the greatest drainage. 

For details of the various river-systems — such as the 
length, area of basin, etc. — see Table, page 174. 



CHAPTER VI. 
Lakes. 

189. Lakes are bodies of water accumulated in 
depressions of the surface of the land. 

They are connected either with the systems of 
oceanic or of inland drainage. The waters of 
lakes draining into the ocean are fresh ; those 
having no connection with the ocean are salt. 

Depth. — From their mode of formation lakes 
which occur in mountainous districts are, as a 
class, deeper than those found on the great low 
plains, since the former occupy the basins of nar- 
row but deep valleys, and the latter the depres- - 
sions of the gentle undulations of the plain. 

In mountainous districts the depths of the depressions 
are sometimes so great that the bottom of the lake is con- 
siderably below the sea-level. Lake Maggiore in the Swiss 
Alps extends about 2000 feet below the level of the sea. 



Lake Superior. 




Fig. 67. Elevations and Depressions of Lakes. 

One of the most remarkable series of depressions in the 
general land-surface of the world is that occupied by the 
waters of Lakes Superior, Michigan, Huron, Erie, and On- 
tario. Superior and Huron, though some 600 feet above 
the level of the ocean, reach, in their greatest depths, far 
below its surface ; the former being 270 feet, and the latter 
about 400 feet, below the general level of the Atlantic. 

When a lake is connected with a river-system, 
the place where the principal stream enters is 
called the head of the lake ; the place where it 
empties is called the foot of the lake. 

190. Geographical Distribution. — The large 



70 



PHYSICAL GEOGRAPHY. 



lake-regions of the world are almost entirely 
confined to the northern continents. 

191. Oceanic Drainage Systems. — North Amer- 
ica contains the most extensive lake-system in the 
world. The lake-region surrounds Hudson Bay, 
and drains into the Arctic through the Mac- 
kenzie; into Hudson Bay through the Sas- 
katchewan ; or into the Atlantic through the 
St. Lawrence. To it belong the Great Lakes — 
Superior, Michigan, Huron, Erie, and Ontario — 





Fig, 68. View on Lake George, N. T. 

embracing a combined area of nearly 100,000 
square miles — and the numerous lakes of Brit- 
ish America. 

Athabasca, Great Slave, and Great Bear Lakes drain 
into the Arctic through the Mackenzie ; Lake Winnepeg, 
into Hudson Bay through the Nelson ; and the Great 
Lakes, into the Atlantic through the St. Lawrence. 

Europe contains two extensive systems of fresh- 
water lakes. The larger region is in Low Europe, 
and surrounds the Baltic Sea and its branches ; 
to it belong Lakes Ladoga and Onega in Russia, 
Wener and Wetter in Sweden, with numerous 
smaller lakes. The smaller region is found in 
the Alps in High Europe. 

Africa contains an extensive system of lakes 
west of the predominant system. Victoria and 
Albert Nyanzas, which drain into the Nile, Lake 
Tanganyika, which drains into the Livingstone 



or the Congo, and Lake Nyassa, which drains 
into the Zambezi, are the principal lakes. 

The remaining continents contain but few large 
fresh-water lakes. In South America we find Lake 
Maracaybo, with brackish water from its vicinity 
to the sea ; and in Asia, Lake Baikal. 

192. The Inland Drainage Systems are inti- 
mately connected with that of inland rivers. The 
term Steppe Lakes and Rivers is generally applied 
to those which have no outlet to the ocean. 

Cause of the Saltness of Inland Waters. — All river- 
water contains a small quantity of common salt and other 
saline substances. Since lakes which have no outlet, or, 
as they are generally called, inland lakes, lose their waters 
by evaporation only, the saline ingredients must be con- 
tinually increasing in quantity ; the water of such lakes 
is therefore generally salt. 

The Dead Sea in Syria is remarkable for the quantity 
of its saline ingredients. In every one hundred pounds 
of its waters there are over twenty-six pounds, or more 
than one-fourth, of various saline ingredients. 

North America. — The largest inland drainage- 
system is in the Great Basin, containing Great 
Salt, Walker, Pyramid, and Owen Lakes. 

South America. — The largest region of inland 
drainage includes the plateau of Bolivia, contain- 
ing Lake Titicaca. The waters of this lake are 
fresh, but have no outlet to the sea, the river form- 
ing the outlet being lost in a salty, sandy plain. 

Europe and Asia contain a vast region of in- 
land drainage extending from the Valdai Hills 
eastward to the Great Kinghan Mountains, em- 
bracing most of the Asiatic plateaus. 

The region contains Lake Elton in Eussia, and the Cas- 
pian and Aral Seas. The combined area of the last two 
is 175,000 square miles. They receive the waters of the 
Volga, the Ural, the Sir, and the Amoo, all large streams. 
Numerous lakes occur on the plateaus. Lake Lop, in the 
depression north of Thibet, receives the Tarim, and Lake 
Hamoou, on the Iranian plateau, the Helmund Eiver. 

Africa contains Lake Tchad in the Soudan, re- 
ceiving the Komadagu and the Shimva, and Lake 
Ngami in Southern Africa. 

Australia contains Lakes Eyre, Torrens, Gaird- 
ner, and Amadeo near the southern coast. 

193. Utility of Lakes. — By offering extended basins 
into which the rivers, when swollen, can disgorge them- 
selves, lakes greatly diminish the destructive effects of 
inundations, often checking them entirely. They afford 
extended surfaces for evaporation, and, collecting the liner 
sediment of the rivers when deserted by their waters, 
form fertile plains. 



— r-3-~65£j£fc_S?a~y>- — 



SYLLABUS. 



71 



SYLLABUS. 



Water is formed by the union of oxygen and hydrogen. 

The waters of the earth may be divided into two classes 
— the continental and the oceanic. 

Water is a solid at and below 32° Fahr., a liquid from 
32° to 212°, and a vapor above 212°. It passes off as vapor, 
however, at all temperatures. 

A pint of water is heaviest at the temperature of 39.2° 
Fahr. Hence in deep lakes, covered with ice, the lower 
layers of water are 7.2° Fahr. above the freezing-point. 

Large bodies of water moderate the extremes of tem- 
perature, because water takes in more heat while warming 
and gives out more on cooling than any other common 
substance. 

During the freezing of a body of water, or the condensa- 
tion of a mass of vapor, considerable stored heat-energy 
appears, or latent heat becomes sensible and warms the 
surrounding air. 

After a body of water has been cooled to the tempera- 
ture of 32° Fahr., it has still 142 heat-units, or pound-de- 
grees, to lose before it can turn into ice. 

After a body of ice has been warmed to the temperature 
of 32° Fahr., it has still 142 heat-units, or pound-degrees, 
of heat to gaiu before it can turn into water. 

Therefore, both freezing and melting are gradual pro- 
cesses. 

The rains cleanse the surface of the earth and purify 
the atmosphere. 

Water is necessary for the existence of life. It forms 
the main food of both animals and plants. 

The atmospheric waters are drained into the ocean 
either by surface or subterranean drainage. 

Springs are the outpourings of the subterranean waters. 

Springs may be classified according to peculiarities in 
the size, shape, and depth of their reservoirs, and the 
nature of the mineral substances composing the strata 
over which the waters flow or iu which they collect. 

According to the size of their reservoirs, springs are 
either constant or temporary. 

If their reservoirs have siphon-shaped outlet tubes, 
their discharges are periodical. 

When their reservoirs are superficial, springs are cold; 
when deep-seated, they are hot or thermal. 

Springs whose waters are moderately cold have their 
reservoirs near the surface. Their lower temperature is 
due to their waters being shielded from the sun. 

Springs with very cold waters have their sources iu the 
melting of large masses of ice or snow. 

Hot or thermal springs owe their high temperature to 
the heat they receive from the interior of the earth. 

Geysers are boiling springs, which, at irregular intervals, 
shoot out huge columns of water with great violence. 

The most extensive geyser regions are those of Iceland, 
New Zealand, and Wyoming. 

Calcareous springs contain lime; silieious, silex; sul- 
phurous, sulphuretted hydrogen and metallic sulphides or 
sulphates ; chalybeate, iron ; brines, common salt ; acidu- 
lous, carbouic acid ; petroleum, coal oil ; bitumiuous, pitch. 

Rivers are fed both by surface and subterranean drain- 
age. 

The main stream with all its tributaries and branches 
is called the river-system. The territory drained into the 
river-system is called the river-basin. The ridge or ele- 
vation separating opposite slopes is called the water-shed. 



In the upper courses of rivers erosion occurs mainly on 
the bottom of the channel ; in the lower courses, at the 
sides. 

In the lower courses of rivers extensive flats or plains 
are found. They are caused by the erosion of the banks 
and the subsequent deposition of fine mud during inunda- 
tions. 

Rivers are constantly at work carrying the mountains 
toward the sea. Through their agency the mean height 
of the continents is decreasing, and their mean breadth 
increasing. 

The eroded material, or silt, may accumulate — 1. In the 
channel of the river ; 2. Along the banks, on the alluvial 
flats or flood-grounds; 3. At the river's mouth; and 4. 
Aloug the coast, near the mouth. 

The accumulations in the channel of the lower Missis- 
sippi have so raised the bed of the stream as to necessitate 
the erection of levees or embankments along the sides. 

Where the tides are weak and the ocean currents absent 
or feeble, the eroded material, or silt, accumulates at the 
mouths of rivers in masses termed deltas. 

The Alps are drained by the Ehine, the Rhone, the Po, 
and the Danube ; these rivers have extensive delta-forma- 
tions. 

The plateau of Thibet is drained by the Hoang-Ho, the 
Yang-tse-Kiaug, the Ganges, the Brahmapootra, and the 
Indus ; all these rivers have extensive delta-formations. 

Among other extensive deltas are those of the Missis- 
sippi, which drains the long slopes of the Pacific and 
Appalachian mountain-systems; the Nile, the Tigris, the 
Euphrates, aud the Zambezi. 

Fluvio-marine formations occur along the coasts ; they 
are caused by the combined action of the river and tides. 

The destruction of forests, by increasing the rapidity of 
drainage, increases the violence of floods. Lakes along 
the river-courses decrease their violence, by allowing the 
torrents to discharge their waters. 

The direction of the drainage of a country is dependent 
on the direction of its slopes. 

The central plain of North America is drained north 
into the Arctic Ocean through the Mackenzie; east iuto 
the Atlantic through the Nelson and the St. Lawrence; 
and south into the Gulf of Mexico through the Mississippi. 

The central plain of South America is drained north 
into the Caribbean Sea through the Magdaleua, east, into 
the Atlantic through the Orinoco aud the Amazon, and 
south, into the Atlantic through the Rio de la Plata. 

The rivers draining the great low plain of Europe rise 
either in the Valdai Hills or on the northern slopes of the 
predominant system. 

Asia possesses the most extended system of inland 
drainage of the continents. Extended systems are also 
found in North America and Europe. 

The Atlantic and the Arctic Oceans drain about three- 
fourths of the continental waters. 

The largest systems of fresh-water lakes occur in North 
America and Europe. 

The Great Lakes of North America occupy remarkable 
depressions iu the continent. The beds of some of them 
are several hundred feet below the level of the sea. 

Lakes without an outlet are salt, because the waters 
they receive contain small quantities of saline ingredients, 
while the waters they lose contain uone. 



72 



PHYSICAL GEOGRAPHY. 



REVIEW QUESTIONS. 



-=-oX*;o 



What is the composition of water? 

Enumerate the physical properties which enable water 
to play so important a part in the economy of the earth. 

What effect has the temperature of the maximum den- 
sity of water on the freezing of large bodies of fresh water ? 
Why? 

How do large bodies of water moderate the extremes of 
heat and cold ? 

Why are freezing and melting necessarily gradual pro- 
cesses ? 

What effect has a heavy rainfall on the temperature of 
the atmosphere? 

Explain the cause of deserts. 

Define subterranean drainage. Surface drainage. 

Upon what does the quantity of water discharged by a 
spring in a given time depend? 

Explain the cause of periodical springs. 

What is the temperature of cold springs? Of hot or 
thermal springs? 

What is the probable cause of the high temperature of 
hot springs? 

How can the probable depth of the reservoir of an arte- 
sian spring be ascertained from the temperature of its 
waters ? 

What are geysers? Explain the cause of their erup- 
tion. 

What is the 'origin of the tube and basin of the geyser? 

Name the three largest geyser regions of the world. 

What is travertine ? How is it formed ? 



Name some of the most important springs from which 
large quantities of salt are obtained. 

What is believed to be the origin of petroleum or coal 
oil? 

How are the precipices of waterfalls caused? In wnat 
courses of a river are they most common ? 

Name the highest waterfall in the world. The grand- 
est. 

Distinguish between an estuary and a delta. 

How does the destruction of the forest increase the 
severity of inundations? 

Upon what does the quantity of water in a river de- 
pend? 

In what different portions of a stream may the silt or 
detritus be deposited? 

What are rafts ? How are they caused ? 

Explain the formation of fluviatile islands and lakes. 

Name some of the most extensive delta-formations in 
North America. In Europe. In Asia. In Africa. 

What is the probable origin of the swamp-lands of the 
Atlantic seaboard? 

How may a tolerably accurate notion of the direction 
of the slopes of a country be obtained by a study of the 
direction of its rivers? 

In what respects do the drainage of North and South 
America resemble each other? 

Name the principal systems of inland drainage of the 
world. 

Explain the cause of the saltness of inland waters. 



MAP QUESTIONS. 



Which ocean drains the largest areas of the continents ? 
Which the smallest ? 

Name the important rivers which drain into the Atlan- 
tic from North America. From South America. From 
Europe. From Africa. 

Name the important rivers which drain into the Pacific 
from North America. From Asia. 

Name the important rivers which drain into the Indian 
Ocean from Africa. - From Asia. From Australia. 

What two systems of inland drainage are there in North 
America? What large region in South America? 

Name an important steppe lake and river in each of the 
continents. 

Describe the region of inland drainage of Europe and 
Asia. What large lakes and rivers belong to this region? 



Describe the regions of inland drainage of Africa. Of 
Australia. Name the important lakes found in each 
region. 

What South American river corresponds in the direction 
of its drainage with the St. Lawrence? With the Mac- 
kenzie? With the Mississippi? 

Name the large rivers which drain the predominant 
mountain-system of Asia. Of Europe. Of Africa. Of 
North America. Of South America. Of Australia. 

Describe the fresh-water lake-region of North America. 
Of South America. Of Europe. Of Africa. 

In which line of trend are most of the fresh-water lakes 
of North America found ? 

Name the Atlantic rivers which have large deltas The 
Pacific rivers. The Indian rivers. 




Section II. 



OCEANIC WATERS. 



CHAPTER I. 
The Ocean. 

194. Composition.- — The water of the ocean 
contains a number of various saline ingredients, 
which give it a batter taste and render it heavier 
than fresh watei in the proportion of 1.027 to 1. 

Every hundred pounds of ocean-water contains 
about three and ione-third pounds of various 
saline ingredients. 

Chloride of sodium, or common salt, chloride of magne- 
sium, sulphates and carbonates of lime, magnesia, and 
potassa, and various bromides, chlorides, and iodides, are 
the principal saline ingredients. 

195. Origin of the Saltness of trie Ocean. — The 
rivers are constantly dissolving from their channels large 
quantities of mineral matters, and pouring them into the 
ocean. Besides this, fully three-fourths of the earth's sur- 
face is covered permauently by the oceanic waters. In 
this way immense quantities of mineral ingredients have 
been dissolved out from the crust. The latter cause was 
especially active during the geological past, when frequent 
convulsions brought fresh portions of the crust into con- 
tact with the warm waters. 

The ocean is Salter in those parts where the evaporation 
exceeds the rainfall, or at about the latitude of the tropics; 
where the rainfall exceeds the evaporation, the water is 
slightly fresher than at the equator. 

In inland seas, like the Mediterranean or the Eed Sea, 
which, though connected with the ocean, yet lose much 
more of their waters by evaporation thau by outflow, the 
proportion of salt is slightly greater than in the ocean. 
In such cases a current generally flows into the sea from 
the ocean. In colder latitudes, inlaud seas, like the Bal- 
tic, receiving the waters of large rivers, contain rather 
less salt than the open sea, and a current generally flows 
from them into the ocean. 

196. Color. — Though transparent and colorless 
in small quantities, yet in large masses the color 
of sea-water is a deep blue. The same is true 
of fresh water. Over limited portions of the 
ocean the waters are sometimes of a reddish or 
a greenish hue, from the presence of numberless 
minute organisms. 

Sometimes a pale light or phosphorescence, 
visible only at night, and due to the presence of 
animalcule, appears where the air comes into con- 
tact with the water, as in the wake of a vessel or 
on the crests of the waves. 



197. Temperature. — The salts dissolved in 
ocean-water lower the temperature of its freez- 
ing-point. Ordinary ocean-water freezes at about 
27° F. In places where the water is Salter, the 
temperature of its freezing-point is lower. 

Ice formed from ocean-water is comparatively 
fresh, nearly all the salt being separated as the 
water freezes or crystallizes. The salt, thus thrown 
out from the frozen water, is dissolved by the 
water below, lowers the temperature of its freez- 
ing-point, and thus increases its density. In this 
manner the water below the ice may have a tem- 
perature lower than that at which the surface- 
water freezes, and yet remain liquid. 

In the polar regions the water below the sur- 
face is at a temperature lower than that of the 
freezing-point of the surface-water. This cold 
water, from its greater density, spreads over the 
floor of the ocean in all latitudes, so that, except 
where stirred by deep currents, the entire bottom 
of the ocean is covered with a layer of dense, 
heavy water, the temperature of which is nearly 
constant. 

The temperature of this water is about 35° F. Near 
the poles it is somewhat lower : about 29°, or a little higher 
than its maximum density of the surface-waters. 

The upper limit of this Une of invariable temperature 
varies with the latitude. Near the equator, where the 
waters are heated to great depths, it is found at about 
10,000 feet below the surface. Toward the poles, it comes 
nearer the surface, reaching it at about Lat. 60°, from 
which point it again sinks, being found at Lat. 70° at 
about 4500 feet below the surface. 

In the tropics the temperature of the surface-water 
is about 80° F. ; in the polar regions it is near the 
freezing-point. The ice which forms in the polar 
regions collects in vast ice-fields or floes. 

198. Shape of the Bottom of the Ocean. — The 
bed of the ocean, though diversified like the sur- 
face of the land, contains fewer irregularities. 
Numerous soundings show that it extends for 
immense distances in long undulations and slopes. 
Its plateaus and plains, therefore, are of great 
size, compared with those of the continents. 
Submerged mountain-ranges occur both in the 
deep ocean and along the shores. The latter 



74 



PHYSICAL GEOGRAPHY. 



belong, properly, to the continental systems of 
elevations. 

199. The Oceanic Areas. — The ocean is one 
continuous body of water, but for purposes of 
description and study it is generally divided into 
five smaller bodies : the Pacific, Atlantic, Indian, 
Arctic, and Antarctic Oceans. The last two are 
separated from the preceding by the polar circles ; 
the others are separated mainly by the continents. 
As the continents do not extend to the Antarctic 
Circle, the meridians of Cape Horn, Cape of 
Good Hope, and South Cape in Tasmania, are 
taken as the ocean boundaries south of these 
points. 

The following table gives the relative size of the oceanic 
areas : 

The Pacific occupies about A the entire water-area. 
" Atlantic " " J " " 

" Indian " " \ " " 

" Antarctic " " fV " " 

" Arctic " " fs 

200. Articulation of Land and Water. — The 
indentations of the oceans, or the lines of junc- 
tion between the water and the land, may be 
arranged under four heads : 

(1.) Inland Seas, or those surrounded by a 
nearly continuous or unbroken land-border; as 
the Gulf of Mexico, Hudson Bay, the Baltic, and 
the Mediterranean, in the Atlantic ; the Red Sea 
and the Persian Gulf, in the Indian ; and the 
Gulf of California, in the Pacific. 

(2.) Border Seas, or those isolated from the 
rest of the ocean by peninsulas and island chains ; 
as the Caribbean Sea, the Gulf of St. Lawrence, 
and the North Sea, in the Atlantic ; and Bering 
Sea, the Sea of Okhotsk, the Sea of Japan, and 
the North and South China Seas, in the Pacific. 

(3.) Gulfs and Bays, or broad expansions of 
the water extending but a short distance into 
the land ; as the Gulf of Guinea and the Bay of 
Biscay, in the Atlantic ; aud the Bay of Bengal 
and the Arabian Sea, in the Indian. 

(4.) Fiords,' or deep inlets, with high, rocky 
headlands, extending often from 50 to 100 miles 
into the land. One of the best instances of this 
form of indentation is off the Norway coast. Ac- 
cording to Dana, fiords are valleys that were ex- 
cavated by vast ice-masses called glaciers, but 
which have since become partially submerged by 
the gradual subsidence of the land. 

Fiord valleys occur on the Norway coast, on 
the coasts of Greenland, Labrador, Nova Scotia, 
and Maine, on the western coast of Patagonia 



and Chili, and on the western coast of North 
America north of the Straits of Fuca. On parts 
of the coast of Greenland the glaciers are now 
cutting out their partially submerged valleys, 
and forming what will probably become fiord 
valleys. 

The Atlantic Ocean is characterized by inland 
seas; the Pacific, by border seas; the Indian, by 
gulfs and bays; the Atlantic and the Pacific, by 
fiords. 

201. Depth of the Ocean. — The mean depth of 
the ocean is about 12,000 ft., or nearly 2k miles. 
Recent soundings give the greatest depth of the 
Atlantic, in the neighborhood of the island of 
St. Thomas of the West Indies, as 27,000 feet. 
The greatest depth in the Pacific, as reported by 
recent careful soundings, occurs east of Japan, 
and is 27,930 ft. These give a depth of about 
5i miles, or less than the greatest elevation of the 
land. It is probable, however, that some portions 
of the ocean are much deeper. 

The greater depressions of the ocean are called 
deeps, the shallower portions are called rises. 

202. The Pacific Ocean.— The shape of the 
shore-line of the Pacific is that of an immense 
oval, nearly closed at the north, but broad and 
open at the south. 

As indicated by the island chains, a number of shallow 
places, or rises, extend in the direction of the north-west 
trend : the summits of those on the north form the Sand- 
wich Islands, and the summits of those on the south form 
the Polynesian Island chain. 

203. The Atlantic Ocean.— The shape of the 
shore-line of the Atlantic is that of a long, 
trough-like valley, with nearly parallel sides. 
The Atlantic has a broad connection with both 
the polar oceans, and forms the only open chan- 
nel for the intermingling of the warm and cold 
waters. 

Shape of the Bed. — Recent soundings in the Atlantic show 
the presence of a submarine plateau extending in mid- 
ocean parallel to the coasts of the continents from the lati- 
tude of the southern point of Africa to Iceland, thus di- 
viding the basin into eastern and western valleys. The 
western valley is the deeper ; the average depths of the two 
being respectively 18,000 and 13,000 feet. A remarkable 



Feet. 


5,000 
10,000 
15,000 



Level of the sea. 



Fig. 69. The Telegraphic Plateau. 



plateau extends across these valleys, from Newfoundland 
to Ireland. Its depth ranges from 10,000 to nearly 13,000 
feet. It is called the Telegraphic Plateau, and bears a 
number of telegraphic cables. The eastern and western 



OCEANIC MOVEMENTS. 



75 



valleys, though less marked in this region, are still dis- 
tinguishable. 

The true bed of the ocean begins at a considerable dis- 
tance from the eastern coast of North America. For dis- 
tances of from 75 to 100 miles, the depth scarcely exceeds 
600 feet ; but from this point it descends, by steep terraces, 
to profound depths. 

The British Isles are connected with the continent of 
Europe by a large submerged plateau, which underlies 
nearly the whole North Sea, and extends for considerable 
distances off the western and southern coasts. The depth 
of this part of the ocean is nowhere very great. 

204. The Indian Ocean.— The shape of the 
shore-line is, in general, triangular. This ocean 
has no connection with the Arctic, but is entirely 
open on the south, where it merges into the great 
water-area of the globe : the basins of the Ant- 
arctic and Pacific. 

Shape of the Bed. — A submarine plateau extends to the 
south off the western coast of Hindostan. Its summits 
form the Laccadive, Maldive, and Chagos Islands, and pos- 
sibly extends in the same direction as far as Kerguelen 
Island. 

205. The Antarctic and Arctic Oceans. — The 
shore-line of the Arctic has the shape of an ir- 
regular ring. The shore-line of the Antarctic is 
probably of the same shape. 

But little is known concerning the beds of these 
oceans. From the very limited land-areas south 
of lat. 50° S., the bed of the Antarctic is presum- 
ably deeper than that of the Arctic, except toward 
the south pole, where it is probably shallower. 

206. Ooze Deposits. — Foraminiferal Land. — 
The reef-forming coral polyps are not the only 
animalculse the accumulation of whose bodies 
after death add to the land-masses of the earth. 
Deep-sea soundings show that over extended areas 



1 



M 



m 



Fig. 70. 




Foraminifera. 



the floor of the ocean is evenly covered with a 
creamy layer of mud or ooze, which, like the 
deposits of the coral animalcules, is composed 
principally of carbonate of lime. This ooze con- 
sists almost entirely of microscopic skeletons of a 



group of animalculse known as the Foraminifera, 
from the great number of perforations or open- 
ings in their hard parts. These animalcule are 
so small that 1,000,000 are equal in bulk to only 
one cubic inch. They appear to live in the layers 
of water near the surface, and after death to 
fall gradually to the bottom of the sea, Sound- 
ings show their presence over very extended 
areas. 

Many of the very deep parts of the ocean's bed 
are covered, not with foraminiferal deposits, but 
with a layer of red mud composed of finely-di- 
vided clay. Its origin is probably as follows : 
In very deep parts of the ocean before the fora- 
miniferal deposits reach the bottom their limey 
matters are dissolved, and the undissolved parts 
form the deposits of fine red mud. 



CHAPTER II. 
Oceanic Movements. 

207. The Oceanic Movements can be arranged 

under three heads : waves, tides, and currents. 

"Waves are swinging motions of the water, 
caused by the action of the wind. Their height 
and velocity depend on the force of the wind, and 
the depth of the basin in which they occur. The 
stronger the wind, and the deeper the ocean, the 
higher the waves and the greater their velocity. 




Fig. 71. Ocean Waves. 

Height of Waves. — Scoresby measured waves in the 
North Atlantic 43 feet above the level of the trough. 
Waves have been reported in the South Atlantic, off the 
Cape of Good Hope, between 50 and 60 feet high. Navi- 



76 



PHYSICAL GEOGRAPHY. 



gators have occasionally reported higher waves, but the 
accuracy of their measurements is, perhaps, to be doubted. 
In the open sea, with a moderate wind, the height of 
ordinary waves is about 6 feet. 

The distance between two successive crests varies from 
10 to 20 times their height. Waves 4 feet high have 
their successive crests 40 feet apart; those 33 feet high, 
about 500 feet apart. 

208. No Progressive Motion of Water in 
Waves. — In wave motion, the water seems to be 
moving in the direction in which the wave is ad- 
vancing, but this is only apparent ; light objects, 
floating on the water, rise and fall, but do not 
move forward with the wave. In shallow water, 
however, the water really advances. The for- 
ward motion of the wave is retarded, so that the 
waves following reach it, thus increasing its 
height. The motion at the bottom is lessened, 
and the top curls over and breaks, producing 
what are called breakers. 

On gently sloping shores, the water which runs down 
the beach, after it has been thrown upon it by the breakers, 
forms, at a little distance from the shore, the dreaded 
" undertow " of our bathing-resorts. 

Force of the Waves. — When high, and moving 
in the direction of the wind, the waves dash 
against any obstacle, such as a line of coast, with 
great force, and may thus cut it away and change 
the coast-line. This action occurs only on ex- 
posed, shelving coasts. The wave-motion is, in 
general, very feeble at 40 feet below the surface. 
The eroding action of the ocean waves is, there- 
fore, far inferior to that of the continental waters. 

209. Tides are the periodical risings and fall- 
ings of the water, caused by the attraction of the 
sun and moon. The alternate risings and fallings 
succeed each other with great regularity, about 
every six hours. Unlike waves, in which the 
motion is confined practically to the surface 
waters only, tides affect the waters of the ocean 
from top to bottom. 

The rising of the water is called flood tide ; the 
falling, ebb tide. When the waters reach their 
highest and lowest points, they remain stationary 
for a few minutes. These points are called, re- 
spectively, high and loiv water. Corresponding 
high or low water, at any place, occurs fifty-two 
minutes later each successive day. 

210. Theory of the Tides. — If the earth were 
uniformly covered with a layer of water, the pas- 
sage of the moon over any place, as at a, Fig. 72, 
would cause the water to lose its globular form, 
become bulged at a, and b, and flattened at c, 
and d. In other words, the water would become 



deeper at a, and b, at the parts of the earth near- 
est and farthest from the moon, and shallower in 




Fig. 72. Lunar Tide, 

all places 90° or at right angles to these points, 
such, for example, as at c, and d. 

This deepening and shallowing of the water is 
caused by the attraction of the moon. As the 
moon passes over a, the water is drawn toward 
the moon, thus deepening the water directly under 
the moon, and shallowing it at c, and d. 

The cause of the deepening of the water at b, 
on the side farthest from the moon, is as follows : 
the solid earth being, as a whole, nearer the moon 
than the water at b, but farther from it than that 
at a, must take a position which will be nearly 
midway between a, and b, leaving a protuberance 
at b, nearly equal to that at a. 

The protuberances a, and b, mark the position 
of high tides. At all pioints of the earth 90° from 
the protuberances, as at c, and d, the depression is 
greatest. These mark the position of loiv tides. 

High tides, then, occur at those points of the 
earth's surface which are cut by a straight line, 
which passes through the centre of the earth and 
that of the attracting body, as the sun or moon. 
Low tides are found at right angles to these 
points. 

Had the earth no rotation, the tidal waves, so 
formed, would slowly follow the moon in its mo- 
tion around the earth. But, by the rotation of 
the eai-th, different parts of its surface are rapidly 
brought under the moon, and the tidal waves, 
consequently, move rapidly from one part of the 
ocean to another. 

Had the moon no motion around the earth, there would 
be two high tides and two low tides every 24 hours. 
While, however, the earth is making one complete rota- 
tion, the moon, in its motion around the earth, has 
changed its position, and the earth rotates for 52 minutes 
longer before the same point again comes directly under 
the moon. 

Since the uniformity of the water surface is 
broken by the elevations of the land, the progress 
of the tidal wave is greatly affected by the size, 
shape, and depth of the oceanic basin, and the 



OCEANIC MOVEMENTS. 



77 



position of the continents. Owing to the obstruc- 
tions offered by the continents, and by inequalities 
in the bed of the ocean, a very considerable re- 
tardation of the tidal wave is effected, so that a 
high tide may not occur at a place until long 
after the moon has passed over it. 

Solar Tides. — -The sun also produces a system 
of tidal waves, but owing, to its greater distance 
from the earth, the tides thus produced are much 
smaller than those of the moon, upon which, there- 
fore, they exert but a modifying influence. The 
tide-producing power of the moon is greater than 
that of the sun, in about the proportion of 800 
to 355. That is_, the tide produced by the moon 
is about 2i times greater than that produced by 
the sun. 

The tidal wave moves, in general, from east to ivest, or in 
the opposite direction to the rotation of the earth. The motion 
of so large a mass of water thus opposed to the earth's ro- 
tation, must gradually diminish the axial velocity, and, 
eventually, entirely stop the rotation of the earth ; in this 
way an increase in the length of day and night should he 
produced, but so far, however, no increase has been de- 
tected, although astronomical observations extend back- 
ward for long periods. The increased axial velocity, pro- 
duced by the contraction of the globe, probably balances 
the retarding influence of the tides. 

In the deep ocean, and near the mouths of rivers, the 
duration of the flood and ebb are about equal ; but in most 
rivers, at some distance from the mouth, the ebb is longer 
than the flood. The cause is to be found in the fact that 
the outflowing river current meets and temporarily neu- 
tralizes the iuflowiug flood tide, thus diminishing its dura- 
tion, and afterward, adding its motion to the ebb, makes 
the difference between the two still greater. 

The tidal wave often ascends a stream to a much greater 
elevation above the level of its mouth than the height of 
the tide at the river's mouth. In large rivers, like the 
Amazon, the tidal wave advances up the river as much as 
100 feet above the sea-level. 



Some of the proofs of the connection between the tides 
and the attraction of the moon and sun are as follows: 

(1.) The interval between corresponding high tides at 
any place is the same as the interval between two succes- 
sive passages of the moon over that place: 24 hours, 52 
minutes. 

(2.) The tides are higher when the moon is nearer the 
earth. 

(3.) The tides are higher when the sun and moon are 
simultaneously acting to cause high tides iu the same 
places. 

Quarter. 




.;: 






1 



■% 



Neap Tides, ■ 

flood and ebb 
moderate. 





Quarter. \^ 

Pig, 73, Cause of the Phases of the Moon, 

Phases of the Moon. — An inspection of Fig. 73 will 
show, that during new aud full moon, the earth, moon, 
and sun are all iu the same straight line, but, that during 
the first and last quarters, they are at right angles. The 
portions of the earth and moon turned toward the sun are 
illumined, the shaded portions are in the darkness. To 
an observer on the earth, the moon, at a, appears new, 
since the dark part is turned toward him ; at b, however, 
it must appear full, since the illumined portions are toward 
him. At c, aud d, the positions of the quarters, only one- 
half of the illumined half, or one quarter, is seen. 



i Spring Tides, 

; flood and ebb 
t excessive. 




Fig. 74. Position of the Earth, Moon, and Snn during Spring and Neap Tides. 



211. Spring and Neap Tides. — -When the sun 
and moon act simultaneously, on the same hemi- 
sphere of the earth, as shown in Fig. 74, the tidal 
wave is higher than usual. The flood tides are 
then highest, and the ebb tides lowest. These 
are called spring tides. They occur twice during 
10 



every revolution of the moon — once at full, and 
once at new moon. The highest spring tides oc- 
cur a short time before the March and the Sep- 
tember equinoxes, when the sun is over the equa- 
tor. 

When, however, the sun and moon are 90° 



78 



PHYSICAL GEOGRAPHY. 



apart, or in quadrature, each produces a tide on 
the portion of the earth directly under it, dimin- 
ishing somewhat that produced by the other body. 
High tide, then, occurs under the moon, while the 
high tide caused by the sun, becomes, by compari- 
son, a low tide. Such tides are called neap tides. 
During their j>revalence, the flood is not very 
high, nor the ebb very low. They occur twice 
during each revolution of the moon, but are low- 
est about the time of the June and December 
solstices. 

The average relative height of the spring tide to that 
of the neap tide is about as 7 to 4. 

212. Birthplace of the Tidal Wave.— Although 
a tidal wave is formed in all parts of the ocean 
where the moon is overhead, yet the " Cradle of 
the Tides " may properly be located in the great 
southern area of the Pacific Ocean. Here the 
combined attraction of the sun and moon origin- 



ate a wave, which would travel around the earth 
due east and west, with its crests north and south; 
but, meeting the channels of the oceans, it is 
forced up them toward the north. Its progress is 
accelerated in the deep basins, and retarded in the 
shallow ones. On striking the coasts of the con- 
tinents, deflected or secondary waves move off in 
different directions, thus producing great com- 
plexity in the form of the parent wave. 

213. Co-Tidal Lines.— The progress of the tidal 
wave, in each of the oceans, is best understood by 
tracing on a ruavj, lines connecting all places 
which receive the tidal wave at the same time. 
These are called co-tidal lines. The distance be- 
tween two consecutive lines represents the time, in 
hours, required for the progress of the tidal wave. 
In parts of the ocean where the wave travels rap- 
idly the co-tidal lines are far apart ; when its prog- 
ress is retarded, they are crowded together. 




Fig. 75. Co-Tidal Chart. 



Since it is only possible to take the height of the tide 
on the coasts of islands and of the. continents, the tracks 
of the co-tidal lines must be to a considerable extent con- 
jectural. 

214. The Pacific Ocean. — Twice every day a 
tidal wave starts in the south-eastern part of the 
Pacific Ocean, west of South America, somewhere 
between the two heavy lines marked xn on the 



chart. It advances rapidly toward the north- 
west in the deep valley of this ocean, reaching 
Kamtchatka in about 6 hours. Toward the west 
its progress is retarded by the shallower water, 
and by the numerous islands, so that it only 
reaches New Zealand in about 6 hours and enters 
the Indian Ocean in about 12 hours. 

215. The Indian Ocean.— The 12-hour-old tidal 



wave from the Pacific, meets and moves along 
with a wave started in this ocean by the moon, 
and advances in the direction indicated by the 
co-tidal lines entering the Atlantic Ocean about 
12 hours afterward. 

216. The Atlantic Ocean. — The tidal wave from 
the Indian joins two other waves, one formed by 
the moor> in this ocean, and the other a deflected 
wave that has backed into the Atlantic from the 
Pacific. The tidal wave thus formed advances 
rapidly up the deep valley of the Atlantic, reach- 
ing Newfoundland 12 hours afterward, or 48 hours 
after it started in the Pacific. It then advances 
rather less rapidly toward the north-east, reach- 
ing the Loffoden Islands 12 hours afterward, or 
60 hours after leaving its starting-place in the 
Pacific. 

217. Tides in Inland Seas and Lakes are very 
small and, consequently, difficult to detect. In 
the Mediterranean Sea the tides on the coasts 
average about 18 inches. The tide in Lake 
Michigan is about If inches. 

218. Height of Tidal Wave. — Ocean tides are 
lowest in mid-ocean, where they range from two 
to three feet. Off the coasts of the continents, 
especially when forced up narrow, shelving bays, 
deep gulfs, or broad river mouths, they attain 
great heights. The cause of these unusual heights 
is evident. When the progress of the tidal wave 
is retarded, either by the contraction of the chan- 
nel or by other causes, the following part of the 
wave overtakes the advanced part, and thus, what 
the wave loses in speed it gains in height, from the 
heaping up of the advancing waters. Where the 
co-tidal lines, therefore, are crowded together on the 
chart, high tides are likely to occur ; for example, 
the Arabian Sea and Bay of Bengal, the North 
and South China Seas, the eastern coasts of Pata- 
gonia, the Bay of Fundy, the English Channel, 
and the Irish Sea, have very high tides. 

Near the heads of the Persian Gulf and China 
Seas, the tides sometimes rise about 36 feet. At 
the mouth of the Severn, the spring tides rise 
from 45 to 48 feet ; on the southern coast of the 
English Channel, 50 feet ; and in the Bay of 
Fundy, near the head, the spring tides, aided by 
favoring winds, sometimes reach 70 feet, and, oc- 
casionally, even 100 feet. 

A strong wind, blowing in the direction in which the 
tidal wave is advancing, causes an increase in the height 
of the tide. 

A low barometer is attended by a higher tide than 
usual ; a high barometer, by a lower tide. 



219. Other Tidal Phenomena. 

The Bore or Eager. — On entering the estuary of a 
river, the volume of whose discharge is considerable, the 
onward progress of the tidal wave is checked ; but, piling 
up its waters, the incoming tide at last overcomes the re- 
sistance of the stream, and advances rapidly, in several 
huge waves. The tides of the Hoogly, the Elbe, the 
Weser, and the Amazon, are examples. In the latter 
river, the wave is said to rise from 30 to 50 feet. 

Races and Whirlpools. — When considerable differ- 
ences of level are caused by the tides, in parts of the ocean 
separated by narrow channels, the waters, in their effort 
to regain their equilibrium, move with great velocity, pro- 
ducing what are called races. At times, several races meet 
each other obliquely, thus producing whirlpools. Near the 
Channel Islands, and off the northern coasts of Scotland, 
races are numerous. The Maelstrom, off the coasts of Nor- 
way, is an instance of a whirlpool, though the motion of 
the waters is not exactly a whirling one. The main phe- 
nomenon is a rapid motion of the waters, alternately back- 
ward and forward, caused by the conflict of tidal currents 
off the Loffoden Islands. 



«>XKo 



CHAPTER III. 
Ocean Currents. 

220. Constant Ocean Currents. — Besides tidal 
currents, the waters of the ocean are disturbed 
to great depths, by currents, moving with consid- 
erable regularity to and from the equatorial and 
polar regions, and thus producing a constant in- 
terchange of their waters. These movements are 
called constant currents, and, unlike waves, con- 
sist in a real, onward movement of the water. 

Constant currents resemble rivers, but are im- 
mensely broader and deeper. As a rule, their 
temperature differs considerably from that of the 
waters through which they flow. They are not 
confined to the surface, but exist as well at great 
depths, when they are called under or counter cur- 
rents, and flow in a direction opposite to that of the 
surface currents. 

221. The Principal Cause of Constant Ocean 
Currents is the difference of density of the water 
produced by the differences of temperature be- 
tween the equatorial and the polar regions. 

As the waters of the polar regions lose their 
heat they become denser, and, sinking to the bot- 
tom, form a mountain-like accumulation of dense, 
cold water, which, as rapidly as formed, spreads 
over the floor of the ocean underneath the lighter 
waters. The consequent lowering of the level of 
the polar waters causes an influx of the surface 
waters from the equatorial regions. In this man- 
ner a constant interchange is effected between the 



80 



PHYSICAL GEOGRAPHY. 



equatorial and polar regions, which, for the greater 
part, takes place along the bottom from the poles 
to the equator, and along the surface from the 
equator to the poles. Since, however, the pole is 
a mere point, this interchange occurs mainly be- 
tween the equator and the polar circles. 




Fig, 76. Currents caused by Difference of Temperature, 

Thus in Fig. 76, the mountain-like accumula- 
tion is shown as having its crest at about the lati- 
tude of the polar circle. The arrows show the 
direction of the currents. At the equatorial re- 
gions, the surface water is warmer and lighter, 
and at the polar regions, probably, colder and 
lighter. 

As a rule, the warm currents are on the surface, and the 
cold currents, from their greater density, are underneath 
them. In shallow oceans, however, the cold currents come 
to the surface, thus displacing the warm currents and de- 
flecting them to deeper parts of the ocean. 

Had the earth no rotation on its axis, this in- 
terchange would be due north and south, or would 
take place directly between the equatorial and 
polar regions. On account of the earth's rota- 
tion, however, and a variety of other causes, 
these north-and-south directions are consider- 
ably changed. The principal of these deflecting 
causes are — ■ 

(1.) The earth's rotation ; 

(2.) The position of the land masses 

(3.) The winds ; 

(4.) Differences of density caused by evapora- 
tion ; 

(5.) Differences of level caused by evapora- 
tion. 

The changes in direction caused hy the earth's rotation 
and the position of the land masses are as follows : as the 
waters are in constant motion, the polar waters reach the 
equatorial regions with an eastward motion less than that 
of the earth. In the equatorial regions, therefore, the 
waters are unahle to acquire the earth's motion toward the 
east, and are left behind ; that is, the earth, slipping from 
under them, causes them to cross the ocean at a, a', Fig. 
77, from east to west, although they are in reality moving 
with the earth toward the east. 

Eeaching the western borders of the oceans, near I, V, 
the continents prevent their going farther west, and de- 
flect them into northern and southern branches, and they 
begin to move toward the poles. 

From c, to d, and from c', to d', the poleward-moving 
waters are deflected toward the east in both hemispheres. 



The waters on reaching c, from o, and J, still retain the 
eastward motion they acquired while moving with the 





Fig. 77. Deflections of Ocean Currents. 

earth. This motion is greater than that of the earth be- 
tween c, and d. Between these points, therefore, the water 
is acted on by two forces, one tending to carry it toward 
the poles, and the other tending to carry it eastward. 
The resultant of these forces carries the water from c, to 
d, and from c', to d', or toward the north-east in the North- 
ern, and toward the south-east in the Southern Hemisphere. 

Between d, and e, and d', and e', the waters still retain 
this excess of eastward motion, and, therefore, move in 
the directions shown. 

Between e, and a, aud e', and a', the waters in both hemi- 
spheres are Reflected toward the west because they are 
unable to acquire the earth's motion toward the east. 
Another, and perhaps the main, cause of this westward 
deflection is the depression caused by the westward move- 
ment of the equatorial waters at a, and a'. 

The action of the wiuds is to tend to move the surface 
waters in the direction in which they are blowing. This 
action is by some authorities regarded as the principal 
cause of constant currents. 

The difference in the density of the water, caused by 
evaporation, leaving the water Salter and denser in some 
parts, and fresher and lighter in others, probably acts to 
some extent as a deflecting cause. For example, the water 
evaporated near the equator, aud precipitated, for the 
greater part, in regions near the borders of the tropics, 
renders the regions Salter and denser from which it was 
evaporated, and fresher and less dense where it is precipi- 
tated. 

The difference in level caused by the greater evapora- 
tion in the equatorial regions north of the equator than 
in corresponding latitudes in the Southern Hemisphere 
has been ascribed as one of the causes of the flow of Ant- 
arctic waters toward the equator. 

222. General Features of Constant Currents. — 
The following motions of the surface currents are 
common to all the three central oceans : 

(1.) A movement of the equatorial waters, a, a, 
from east to west ; 

(2.) Their deflection into northern and south- 
ern branches (b and c), on reaching the western 
borders of the ocean ; 

(3.) A movement of the waters beyond the 
equator from west to east (d, e) ; 



Page 81. 




82 



PHYSICAL GEOGRAPHY. 



(4.) A separation of these latter currents into 
two branches (/, g and h, i), one continuing toward 




a— Equator. 



Fig. 78, Chart of Constant Currents. 

the poles, and the other toward the equator, where 
they join with the equatorial currents, thus com- 
pleting a circuit in the shape of a vast ellipse ; 

(5.) A flow of the Arctic waters along the 
western border of the ocean (J), and of the Ant- 
arctic along the eastern (Jc). 

Since the Indian Ocean is completely closed on the 
north, only part of the above movements are observed. 
In the Pacific, an equatorial counter-current crosses the 
ocean from west to east. 

223. Currents of the Atlantic. — The equatorial 
current crosses the ocean, from east to west, in 
two branches : a south equatorial current, which 
comes from the Antarctic, and a north equatorial 
current, which comes mainly from regions north 
of the equator. 

The north equatorial current flows along the 
northern coast of South America, and, separating, 
part of it enters the Caribbean Sea and Gulf of 
Mexico, and part flows north, passing east of the 
Bahamas. 

The Gulf Stream flows along the eastern coast 
of North America, with a velocity of from four to 
five miles per hour, and in mid-ocean, between 
Newfoundland and Spain, divides, one branch 
flowing toward Norway, Spitzbergen, and Nova 
Zembla, the other flowing southward, down the 
coasts of Africa, where it forms the main feeder 
. of the north equatorial current. 

The south equatorial current, after crossing the 
ocean, flows south along the Brazilian coast, and 
divides near Rio Janeiro, the main part flowing 
eastward and mingling with the Antarctic cur- 
rent, and the remainder continuing down the east- 



ern coast of South America. Cold currents from 
the Arctic flow down the coasts of Greenland and 
Labrador. A broad polar current sweeps from 
the Antarctic Ocean, and forms the main feeder 
of the south equatorial current, but passes in 
greater part eastward, south of Africa. 

A small elliptical current flows near the equator, 
between the north and south equatorial currents. 

224. Currents of the Pacific. — North and south 
equatorial currents flow from east to west, and 
between them a smaller, less powerful equatorial 
counter-current, from west to east. The south 
equatorial current, fed by the broad Antarctic 
current, is the larger of the two. 

The north equatorial current, on reaching the 
Philippine Islands, divides into northern and 
southern branches ; a portion of its southern 
branch returns with the equatorial counter-cur- 
rent, while the northern branch, the main por- 
tion, flows north-east along the Asiatic coast as 
the Kuro Sivo, the counterpart of the Gulf 
Stream. At about Lat. 50°, this flows east- 
wardly as a North Pacific current, and off the 
shores of North America it returns, in an ellip- 
tical path, southerly to the north equatorial cur- 
rent, forming its main feeder. A small current 
flows through the eastern side of Bering Strait, 
into the Arctic Ocean. 

The south equatorial current of the Pacific is 
broken into numerous branches during its passage 
through the islands in mid-ocean. Reaching the 
Australian continent and the neighboring archi- 
pelagoes, it sends small streams toward the north, 
but the main portion flows south, along the Aus- 
tralian coast, when, flowing eastward, it merges 
with the cold Antarctic current. 

The Antarctic current moves as a broad belt 
of water toward the north-east, when, flowing up 
the western coast of South America, it turns to 
the west, and forms the main feeder of the south 
equatorial current. A part of the Antarctic cur- 
rent flows eastward, south of South America, and 
enters the Atlantic as the Cape Horn current. 

A small cold current from the Arctic flows 
through Bering Strait, down the Asiatic coast. 

225. Currents of the Indian Ocean, — Only a 
south equatorial current exists, which flows down 
the eastern and western coasts of Madagascar, and 
down the African coast to Cape Agulhas, when, 
turning eastward, it merges with the Antarctic 
current, and flows up the western coast of Aus- 
tralia, where it joins the equatorial current. 



SYLLABUS. 



83 



The north equatorial current in this ocean is indistinct — 

(1.) Because the ocean has no outlet to the north ; 

(2.) Powerful seasonal winds, called the monsoons, move 

the waters alternately in different directions, as huge drift 

currents. 

Sargasso Seas. — Near the centre of the ellip- 
tical movement in each of the central oceans, 
masses of seaweed have collected where the water 
is least disturbed. These are called sargasso seas. 



226. Utility of Currents : 

(1.) They moderate the extremes of climate by 
carrying the warm equatorial waters to the poles, 
and the cold polar waters to the equator ; 

(2.) They increase materially the speed of ves- 
sels sailing in certain directions ; 

(3.) They transport large quantities of timber 
to high northern latitudes. 



SYLLABUS. 



Ocean water contains about three and one-third pounds 
of various saline ingredients, in every one hundred. Chlo- 
ride of sodium ; sulphates and carbonates of lime, mag- 
nesia, and potassa; and various chlorides, bromides, and 
iodides, are the principal saline ingredients. 

The salt of the ocean is derived either from the 
washings of the land, or is dissolved out from the por- 
tions of the crust which are continually covered by its 
waters. 

The ocean is Salter in those parts where the evaporation 
exceeds the rainfall. Seas like the Mediterranean, which 
are connected with the ocean by narrow channels, and in 
which the evaporation is greater than the rainfall, are 
Salter than the ocean. Others, like the Baltic, in which 
the rainfall exceeds the evaporation, are fresher than the 
ocean. 

Most of the bed of the ocean is covered with a layer of 
dense water, at about the temperature of its maximum 
density. 

The Pacific and Atlantic Oceans occupy about three- 
fourths of the entire water-area of the earth. 

South of the southern extremities of South America, 
Africa, and Australia, the meridians of Cape Horn, Cape 
Agulhas, and South Cape in Tasmania, are assumed as 
the eastern boundaries of the Pacific, Atlantic, and Indian 
Oceans. 

The articulation of land and water assumes four distinct 
forms : Inland Seas, Border Seas, Gulfs and Bays, and Fiords. 
Inland Seas characterize the Atlantic; Border Seas, the Pa- 
cific; Gulfs and Bays, the Indian Ocean; and Fiords, the 
Atlantic and Pacific. 

The telegraphic plateau lies between Ireland and New- 
foundland. Its average depth is about two miles. 

The bottom of the ocean is not as much diversified as 
the surface of the land. Its plateaus and plains are be- 
lieved to be much broader than are those of the land. The 
profound valleys of the ocean are called deeps, its shallow 
parts, rises. 

The greatest depth of the ocean that has as yet been 
accurately sounded is about 51 miles. It is probably deeper 
than this in some places. 

Over extended areas, the floor of the ocean is uniformly 
covered with a deposit of fine calcareous mud or ooze, 
formed of the hard parts of the bodies of minute animal- 
culae. 

The movements of the oceanic waters may be arranged 
under the three heads: waves, tides, and currents. 



The height and velocity of a wave depend upon the 
force of the wind and the depth of the oceanic basin. 

In ordinary wave motion, the water rises and falls, but 
does not move forward. 

Tides are the periodical risings and fallings of the water, 
caused by the attraction of the sun and moon. 

The rising of the water is called flood tide ; the falling, 
ebb tide. 

If the earth were uniformly covered with a layer 
of water, two high tides would occur simultaneously; 
one on the side of the earth directly under the sun 
or moon, the other on the side farthest from the sun 
or moon. 

The tidal wave crosses the ocean from east to west, fol- 
lowing the moon in the opposite direction to that in which 
the earth passes under it while rotating. Its progress is 
considerably retarded by the projections of the continents, 
and the shape of the oceanic beds. Had the moon no real 
motion around the earth, there would be two high and 
two low tides every twenty-four hours, or the high and 
low tides would be exactly six hours apart. 

Spring Tides are caused by the combined attractions of 
the sun and moon on the same portions of the earth. Neap 
tides by their opposite attractions. 

The parent tidal wave is considered as originating in 
the great water-area of the Pacific on the south. 

Co-tidal lines are lines connecting places which have 
high tides at the same time. 

When the progress of the tidal wave is retarded by the 
shelving coast of a continent, what the tide loses in speed, 
it gains in height. The highest tides, therefore, occur 
where the co-tidal lines are crowded together. 

Bores, Paces, and Whirlpools are tidal phenomena. 

Oceanic currents are either temporary, periodical, or 
constant. 

The heat of the sun and the rotation of the earth are 
the main causes of constant oceanic currents. 

The followii-g peculiarities characterize the constant 
currents in the three central oceans: 

(1.) A flow in the equatorial regions from the east to 
the west; 

(2.) A flow in extra-tropical regions from the west to 
the east; 

(3.) A division of the eastwardly flowing extra-tropical 
waters in mid-ocean into two branches; one of which 
flows toward the poles, and the other toward the equator 
where it merges into the equatorial currents. 



84 



PHYSICAL GEOGRAPHY. 



The principal cause of constant ocean currents is the 
difference in the density of the equatorial and polar 
waters, produced by differences of temperature. 

The cold, dense waters of the polar regions tend to mix 
with the warm, light waters of the equatorial regions 
along due north-and-south lines. This tendency to north 
and south direction is prevented by the following causes: 

(1.) The rotation of the earth ; 

(2.) The position of the continents: 

(3.) The direction of the winds ; 

(4.) The difference in the saltness of the water; 

(5.) The inequality of the evaporation and rainfall. 



In the Pacific, a counter-current crosses the ocean in the 
equatorial region, from west to east. 

In the Indian Ocean, the directions of the currents are 
modified by the laud masses, which surround the northern 
part of its bed. 

In the northern hemispheres, the western borders of the 
oceans are colder than the eastern borders in the same lati- 
tude, because the former receive the polar currents and the 
latter the equatorial. 

Currents moderate the extremes of climate, by carry- 
ing the warm equatorial waters to the poles, and the cold 
polar waters to the equator. 



REVIEW QUESTIONS. 



How much heavier is salt water than fresh water ? 

What is the freezing-point of ocean water? 

Explain the origin of the saltness of the oceanic waters. 

In the equatorial region, where is the water the colder, 
at the surface or near the bottom of the ocean ? 

How do the areas of the Pacific and Atlantic compare 
with each other in size? Of. the Antarctic and Arctic? 

Define inland sea; border sea; gulf or bay; fiord; give 
examples of each. 

Define deeps ; rises. 

What, most probably, is the shape of the bed of the At- 
lantic? Of the Pacific? Of the Indian Ocean ? 

Describe the Telegraphic Plateau. 

How does the greatest depth of the ocean compare with 
the greatest elevation of the land ? 

Upon what does the height of a wave depend ? On what 
does its velocity depend? 

What proof is there that during wave motion in deep 
water there is no continued onward motion of the water? 

Distinguish between ebb and flood tides. 

What proofs have we that tides are occasioned mainly 
by the attraction of the moon ? 

What are spring tides? Neap tides? During what 
phases of the moon do they each occur? 



Why should the moon, which is so much smaller than 
the sun, exert a more powerful influence in producing 
tides? 

Where does the parent tidal wave originate? 

What are co-tidal lines? 

Why does the tidal wave progress from east to west? 

Explain the nature of the influence which the tidal 
wave exerts on the rotation of the earth. 

In what parts of the ocean will unusually high tides 
occur ? Why ? 

By what are races and whirlpools occasioned? 

Distinguish between temporary, periodical, and constant 
oceanic currents. 

Explain the origin of constant currents. How are the 
directions of constant currents affected by the rotation of 
the earth and the shapes of the continents ? 

What features of constant currents are common to each 
of the three central oceans ? 

Ou which side of the northern oceans do the polar cur- 
rents flow? On which side of the southern oceans? 

What are sargasso seas ? How are they formed ? 

What effect is produced by ocean currents on the ex- 
tremes of climate? 

Of what value are ocean currents to navigation ? 



MAP QUESTIONS. 



-°hd>©<o 



Point out, on the map of the river-systems, the inland 
seas of the Atlantic ; of the Pacific ; of the Indian Ocean. 

Point out the border seas of the Atlantic; of the 
Pacific. 

Point out the gulfs or bays of the Atlantic ; of the In- 
dian Ocean. 

Point out the principal regions of fiords. 

How many hours does it take the tidal wave to progress 
from Tasmania to the Cape of Good Hope? From Tasma- 
nia to Newfoundland? From Tasmania to the British 
Isles? (See map of the co-tidal lines.) 

In what parts of the Atlantic does the tidal influence 
progress most Tapidly? 

If the velocity of any kind of wave motion in water in- 
creases with the depth of the basin, what parts of the At- 
lantic appear to be the deepest? What portions of the 
Pacific? What portions of the Indian Ocean? 

Trace on the map of the ocean currents, the motion 
of the Antarctic currents in each of the three central 
oceans. 



Where is the Cape Horn current? Is it hot or cold? 
What points of resemblance exist between the north 
and south equatorial currents in the Atlantic and Pacific 
Oceans ? 

Trace the progress of the Gulf Stream. 

What points of resemblance exist between the Gulf 
Stream and the Japan current? 

How far to the north-east do the waters of the Gulf 
Stream extend? 

What distant shores are warmed by the waters of the 
Gulf Stream? By those of the Japan current? 

Why do not the heated waters of the Gulf Stream exert 
a more powerful influence on the climate of the eastern 
sea-board of the United States? 

Point out the principal cold currents; the principal 
warm currents. 

Which currents would aid, and which would retard, the 
progress of a vessel in sailing from New York to San Fran- 
cisco? From America to Europe? From America to India 
or Australia ? 



Part IV. 

THE ATMOSPHERE. 



oXKo 



^sSfe^. 




We live at the bottom of a vast ocean of air, which, like the ocean of water, is subject to three 
general movements — waves, tides, and currents. By means of waves, its upper surface is heaved in 
huge mountain-like masses in one place, and hollowed out in deep valleys in another. By means of 
currents, circulatory movements are set up, which effect a constant interchange between the air of the 
equatorial and the polar regions. By means of tides, the depth of the atmosphere is increased in some 
places and decreased in others. 

Of these three movements of the atmosphere, currents are of the greatest importance. Aerial cur- 
rents, or winds, are similar to oceanic currents, but are more extensive and rapid, owing to the greater 
mobility of air. 

By retaining and modifying the solar heat, absorbing and distributing moisture, supplying animals 
with oxygen and plants with carbonic acid, the atmosphere plays an important part in the economy 
of the earth. 

Meteorology is the science which treats of the atmosphere and its phenomena. 



Section I. 



THE ATMOSPHERE. 



•«*;o 



CHAPTER I. 

General Properties of the Atmo- 
sphere. 

227. Composition. — The atmosphere is a me- 
chanical mixture of nitrogen and oxygen, in the 



proportion, by weight, of nearly 77 per cent, of 
nitrogen to 23 per cent, of oxygen. To these 
must be added a nearly constant quantity of car- 
bonic acid, about 5 or 6 parts in every 10,000 
parts of air, or about a cubic inch of carbonic acid 
to every cubic foot of air, and a very variable pro- 

85 



86 



PHYSICAL GEOGKAPHY. 



portion of watery vapor. The gaseous ingredients, 
though of different densities, are found in the 
same relative proportions at all heights, owing 
to a property of gases called diffusion. 

The oxygen and carbonic acid are the most important 
of the gaseous constituents. Oxygen supports combustion 
and respiration, and is thus necessary to the existence of 
animal life. Carbonic acid, composed of carbon and oxy- 
gen, is the source from which vegetation derives its woody 
fibre, and is thus necessary to the existence of plant life. 
In respiration, animals take in oxygen and give out car- 
bonic acid ; in sunlight, plants take in carbonic acid and 
give out oxygen. In this way the relative proportions of 
the substances necessary to the existence of animal and plant 
life are kept nearly constant. 

228. Elasticity. — The atmosphere is eminently 
elastic ; that is, when comjjressed, or made to oc- 
cupy a smaller volume, it will regain its original 
volume on the removal of the pressure. Air also 
expands when heated and contracts when cooled. 

229. Pressure. — So evenly does the atmosphere 
press on all sides of objects that it was long be- 
fore it was discovered that air possesses weight. 
The discovery was made by Torricelli, an Italian 
philosopher and pupil of the famous Galileo. The 
instrument Torricelli employed is called a Ba- 
rometer. 




Fig. 79. Barometer. 

230. The Barometer.— The principle of the barometer 
is as follows : A glass tube, about 33 inches in length, is 
closed at one end and filled with pure mercury. Placing 
a finger over the open end, the tube is reversed and dipped 
below the surface of mercury in a cup or other vessel. 
On removing the finger, a column of mercury remains in 
the tube, being sustained there by the pressure of the at- 
mosphere. Near the sea-level this column is about 30 
inches high ; on mountains it is much lower ; in all cases, 
the weight of the mercurial column being equal to that 
of an equally thick column of air, extending from the 
level of the reservoir to the top of the atmosphere. 

Any variation in the pressure of the atmosphere is 
marked by a corresponding variation in the height of the 
mercury in the barometer, the column rising with in- 
creased, and falling with diminished, pressure. 

The entire atmosphere presses on the earth 



with the same weight as would a layer of mer- 
cury about 30 inches in depth. A column of 
mercury 30 inches high, and one square inch in 
area of cross section, weighs about 15 pounds. 
Therefore, the pressure which the atmosphere exerts 
on the earth's surface, at the level of the sea, is equal 
to about 15 pounds for every square inch of surface. 
The entire weight of the atmosphere, in pounds, 
is equal to 15 times the number of square inches 
in the earth's surface. 

The atmospheric pressure is not uniform on all parts of 
the earth at the same level. From a few degrees beyond 
the equator the pressure increases in each hemisphere up 
to about lat. 35°, where it reaches its maximum, decreasing 
in the northern hemisphere to lat. 65°, when it again in- 
creases toward the poles. 

231. Height of the Atmosphere. — If the air 
were everywhere of the same density, its height 
could be easily calculated ; but, on account of its 
elasticity, the lower layers are denser than the 
others, because they have to bear the weight of 
those above them. The density must, therefore, 
rapidly diminish as we ascend. 

If by pressure on a gas we diminish its volume one- 
half, its density will be doubled ; conversely, if the den- 
sity be diminished one-half, the volume will be doubled. 
The following table, calculated from the law of increase 
in volume with diminished pressure, gives the barometric 
height, the volume, and the density of the air at different 
elevations above the sea. The elevation of 3.4 miles is the 
result of observation ; the other distances are estimated. 



Barometric 


Vol. of Given 


Density. 


Estimated Distance 


Height in Inches. 


Weight of Air. 


ab. Sea, in Miles. 


30.00 


1 


1 


0.0 


15.00 


2 


i 


3.4 


7.50 


4 


i 


6.8 


3.75 


8 


1 


10.2 


1.87 


16 


rV 


13.6 


.93 


32 


& 


17.0 



It appears from the above table that by far the 
greater part of the air by weight lies within a few 
miles of the surface, nearly three-fourths being 
below the level of the summits of the highest 
mountain-ranges. 

The height of the upper limit of the atmosphere 
has been variously estimated. Calculations based 
upon the diminution of pressure with the height, 
place it at from 45 to 50 miles above the level of 
the sea ; others, based on the duration of twilight, 
place it at distances varying from 35 to 200 miles. 

The form of the atmosphere is that of an ob- 
late spheroid, the oblateness of which is greater 
than that of the earth. 




By carefully observing the decrease in pressure with the 
elevation, at different altitudes, and making proper correc- 
tions, the heights of mountains can be readily determined 
by the barometer. The measurement of heights by the 
barometer, or similar means, is called Hypsometry. 



oKXo 



CHAPTER II. 

Climate. 

232. The Climate of a country is the condi- 
tion of its atmosphere as regards heat or cold. 

The climate of a country also embraces the con- 
dition of the air as regards moisture or dryness, 
and healthiness or unhealthmess, which are de- 
pendent on the temperature. 

233. Temperature. — The temperature of the 
atmosphere is determined by means of an instru- 
ment called a thermometer. 

The thermometer consists of a glass tube of very fine 
bore, furnished at one end with a bulb. The tube is care- 
fully dried and the bulb filled with pure mercury and 
heated in the flame of a spirit-lamp ; the mercury expands, 
and, filling the fine capillary tube, a portion runs out 
from the open end, thus effectually expelling the air. A 
blowpipe flame is then directed against the open end and 
the tube hermetically sealed. As the bulb cools, the mer- 
cury contracts, and leaves a vacuum in the upper part of 
the tube. The instrument will now indicate changes in 
temperature; for, whenever the bulb grows warmer, the 
column of mercury expands and rises ; and when it grows 
colder, it contracts and falls. 

In order to compare these changes of level they are 
referred to certain fixed or standard points : the freezing- 
and boiling-points of pure water. These are obtained by 
marking the respective heights to which the mercury rises 
when the thermometer is plunged into melting ice and 
into the steam escaping from boiling water. In Fahren- 
heit's scale the freezing-point is placed at 32°, the boil- 
ing-point at 212°, and the space between these two points 
divided into 180, (212 — 32) equal parts, called degrees. In 
the Centigrade scale the freezing- and boiling-points are re- 
spectively 0° and 100°. Fahrenheit's degrees are repre- 
sented by an F., thus, 212° F. ; Centigrade's by a C, as 
100° c. 

234. Astronomical and Physical Climates. — 

Astronomical climate is that which would result 
were the earth's surface entirely uniform and of 
but one kind : all land or all water. 

Physical climate is that which actually exists. 

Since the physical climate is only a modification of the 
astronomical, we shall briefly review the causes which 
tend to produce a regular decrease in temperature from 
the equator to the poles. 

Astronomical Climate. — The sun is practically 
the only source of the earth's heat. On account 
of the earth's spherical shape, those portions of 



the surface are most powerfully heated which re- 
ceive the vertical rays, and these are confined to 
a zone reaching 23° 27' on each side of the equa- 
tor. Beyond these the rays fall with an obliquity 
which increases as we approach the poles. 

235. Causes of the greater heating power of 
the vertical rays of the sun than of the oblique 
rays. 

lb 




Fig, 80. Causes of the Greater Heating Power of the Vertical 
than of the Oblique Kays, 

(1.) The vertical rays are spread over a smaller 
area. Equal areas of the sun's surface give off 
equal quantities of heat. If, therefore, the bun- 
dle of rays a b, and c d, come from equal areas, 
the amounts of heat they emit will be equal ; but 
while the heat given off from a b, the more ver- 
tical rays, is spread over the earth's surface from 
/, to g, that from c d, is spread over the greater 
area h i; the area / g, therefore, which receives 
the more vertical rays, is much warmer than h i, 
where the obliquity is greater. 

(2.) The vertical rays pass through a thinner 
layer of air. Only a part of the sun's heat 
reaches the surface of the earth ; about 28 per 
cent, of the vertical rays are absorbed during their 
passage through the atmosphere. The amount of 
this absorption must increase as the length of 
path increases. In the figure, the light shading 
represents the atmosphere. It is clear that the 
oblique rays pass through a thicker stratum of 
air than the more direct ones, and, therefore, are 
deprived of a greater amount of heat. 

According to Laplace, the thickness of the stratum of air 
traversed by the rays when the sun is at the horizon is 
35.5 times greater than when it is directly overhead. A 
similar absorption of light affects the comparative bright- 
ness of daylight in different latitudes. 

(3.) The vertical rays strike more directly, 
and, therefore, produce more heat. The heating 



Page 3d. 




CLIMATE. 



89 



power of the more nearly vertical rays is greater 
than that of the rays which strike obliquely. 

236. Variations in Temperature. — The differ- 
ences in the heating power of the vertical and ob- 
lique rays of the sun cause the temperature of 
the earth's surface to decrease gradually from the 
equator toward the poles. The differences of tem- 
perature thus effected are further increased by the 
difference in the length of daylight and darkness. 
While the sun is shining on any part of the earth 
the air is gaining heat ; when it is not shining the 
air is losing heat. When the length of daylight 
exceeds that of the darkness, the gain exceeds 
the loss; when the darkness exceeds the day- 
light, the loss exceeds the gain. 

The excessively low temperatures that would 
result from the oblique rays in high latitudes are 
prevented by the great length of daylight during 
the short summers, thus allowing the sun to con- 
tinue heating the surface during longer periods. 
The warmest part of the day in high latitudes 
sometimes equals that in the equatorial regions. 
During the long winters, however, the continued 
loss of heat makes the cold intense. 

Hence in the tropics we find a continual sum- 
mer ; in the temperate zones, a summer and winter 
of nearly equal length; and in the polar zones, 
short, hot summers, followed by long, intensely cold 
winters. 

The true temperature of the air is ascertained by hang- 
ing a thermometer a few feet above the ground, so as to be 
shielded from the direct rays of the sun, and yet be in free 
contact on all sides with the air. 

237. Manner in which the Atmosphere re- 
ceives its Heat from the Sun. — The atmosphere 
receives its heat from the sun — 

(1.) Directly. As the sun's rays pass through 
the air, about 28 per cent, of the vertical rays 
are directly absorbed, thus heating the air. The 
remainder pass on and either heat the earth, or 
are reflected from its surface. 

(2.) From the heated earth. The sun's rays 
heat the earth and the heated earth heats the air. 
It does this in three ways : 

(a.) By the air coming in contact with the 
heated earth. 

(6.) By the heated earth radiating its heat, or 
sending it out through the air in all directions. 

After the sun's heat has been absorbed by the 
earth and radiated from it, a change occurs which 
renders the rays much more readily absorbed by 
the air. 

(e.) By the heat being reflected from the earth 
11 



and again sent through the air. But little heat 
is imparted to the air in this way. 

It is mainly the aqueous vapor the atmosphere 
contains that absorbs the sun's heat. Dry air 
allows the greater part of the heat to pass through 
it ; therefore variations in the quantity of vapor in 
the air must necessarily produce corresponding 
variations in the distribution of heat. 

238. Isothermal Lines are lines connecting 
places on the earth which have the same mean 
temperature. 

The Mean Daily Temperature of a place is ob- 
tained by taking the average of its temperature 
during twenty-four consecutive hours. 

The Mean Annual Temperature of a place is 
the average of its mean daily temperature 
throughout the year. 

If the physical climate were the same as the 
astronomical, the isothermal lines would coincide 
with the parallels of latitude. 

An inspection of the map of the isothermal lines shows 
that their deviations from the parallels, though well 
marked in all parts of the earth, are greatest m the north- 
ern, hemisphere. Wherever, from any cause, the mean tem- 
perature of a place is higher, the isothermal lines are found 
nearer the poles; when lower, nearer the equator. The former 
effects are noticed particularly in portions of the ocean 
traversed by warm currents ; the latter, in crossing por- 
tions of the ocean traversed by cold currents. In the map 
of the isothermal lines the influence of elevation is re- 
moved by adding 1° for every 1000 feet of elevation. 

239. Physical Zones. — The Physical Torrid 
Zone lies on both sides of the equator, between 
the annual isotherms of 70° Fahr. 

The Physical Temperate Zones lie north and 
south of the Physical Torrid Zone, between the 
annual isotherms of 70° and 30° Fahr. 

The Physical Frigid Zones lie north and south 
of the Physical Temperate Zones, from the an- 
nual isotherms of 30° Fahr. to the poles. 

The greatest mean annual temperature in the 
eastern hemisphere is found in portions of North 
Central Africa, and in Arabia near the Red Sea, 
in the southern part of Hindostan, and in the 
northern part of New Guinea and the neighbor- 
ing islands; in the western hemisphere, in the 
northern parts of South America and in Central 
America, 

240. Modifiers of Climate. — The principal 
causes which prevent the isothermal lines from 
coinciding with the parallels of latitude are: 

(1.) The Distribution of the Land and Water 
Areas. — Land heats or cools rapidly, absorbing or 
emitting but little heat. This is because the land 



90 



PHYSICAL GEOGRAPHY. 



has a small capacity for heat, and also because 
the heat passes through but a comparatively thin 
layer. Therefore, a comparatively short exposure 
of land to heat produces a high temperature, and 
a conrparatively short exposure to cooling, a low 
temperature. Water heats or cools slowly, ab- 
sorbing or emitting large quantities of heat. This 
is because water has a great capacity for heat. 
The heat penetrates a comparatively deep layer, 
and then, too, as soon as slightly heated, the warm 
water is replaced by cooler water. Therefore, the 
water can be exposed to either long heating or 
long cooling without growing very hot or very 
cold. Hence, the land is subject to great and 
sudden changes of temperature; the water, to 
small and gradual changes. 

Places situated near the sea have, therefore, a 
more equable, uniform climate than those in the 
same latitude in the interior of the continent. 
The former are said to have an oceanic climate ; 
the latter, a continental climate. 

In the polar regions, a preponderance of moder- 
ately elevated land areas causes a colder climate than 
an equal area of water, because land loses heat 
more rapidly than water. 

In the tropics, a preponderance of land areas 
causes a warmer climate than an equal area of water, 
because land gains heat more rapidly than water. 

(2.) The Distribution of the Relief Forms of 
the Land Masses. 

(1.) Elevation. — The temperature of the atmo- 
sphere rapidly decreases with the elevation. The 
decrease is about 3° Fahr. for every 1000 feet. 

The increased cold is caused as follows : 

(1.) Since the air receives so much of its heat indirectly 
from the earth's surface, the farther we go upward from 
the surface, the colder it grows. 

(2.) In the upper regions of the atmosphere the de- 
creased density and humidity of the air prevent it from ab- 
sorbing either the direct rays of the sun, or those reflected 
or radiated from the earth. The effect of elevation is so 
powerful that on the sides of high tropical mountains the 
same changes occur in the vegetation that are observed in 
passing from the equator to the poles. 

(2.) Direction of the Slopes. — That slope of 
an elevation on which the sun's rays fall in a di- 
rection the more nearly at right angles to its sur- 
face will be the warmest. 

In the northern hemisphere the southern slope of a hill 
is warmer in winter than the northern slope, because the 
rays fall more nearly at right angles to its surface. 

(3.) Position of the Mountain-Ranges. — A 
mountain-range will make the country near it 
warmer if the wind from which it shields it is 



cold ; it will make it colder if such wind is 
warm. 

The position of the mouutaiu-ranges of a country also 
greatly affects the distribution of its rainfall. Thus, the 
tropical Andes are well watered and fertile on their east- 
ern slopes, but dry and barren on their western. The pre- 
vailing moist trade winds, forced to ascend the slopes, 
deposit all their moisture on them in abundant showers, 
and are dry and vaporless when they reach the other side, 

(4.) Nature of the Surface. — The temperature 
of a tract of land is greatly affected by the nature 
of its surface. If covered with abundant vege- 
tation, like a forest, or if wet and marshy, its sur- 
face heats and cools slowly, and has a compara- 
tively uniform temperature ; but if destitute of 
vegetation, and dry, sandy, or rocky, it both 
heats and cools rapidly, and is subject to great 
extremes of temperature. 

(3.) Distribution of Winds and Moisture. — The 
principal action of the winds, and their accom- 
panying moisture, is to moderate the extremes of 
temperature by the constant interchange between 
the heat of the equatorial and the cold of the 
polar regions. Both wind and vapor absorb and 
render latent large quantities of heat in the equa- 
torial regions, and give it out, in higher latitudes, 
on cooling. In cold countries the climate is ren- 
dered considerably warmer by the immense quan- 
tity of heat thus emitted by the condensed vapor. 

(4.) Ocean Currents. — Since the warm waters 
move to the polar regions, and the cold waters to 
the equatorial regions, the general effect of ocean 
currents on climate is to reduce the extremes of 
temperature. 

The combined effects of the action of the winds, 
moisture, and ocean currents are seen in the north- 
ern continents, whose western shores, under the in- 
fluence of the prevailing south-westerly winds, 
copious rains, and tropical currents, are consider- 
ably warmer than the eastern shores in the same 
latitude. ^ 

The coasts of Great Britain are warm and fertile, while 
Labrador, in the same latitude, is cold and sterile. The 
island of Sitka, in the Pacific, is warmer thau Kamtchatka 
from similar causes. 



«*» 



CHAPTER III. 



The Winds. 



241. Origin of Winds. — Winds are masses of 
air in motion. They resemble currents in the 
ocean, and result from the same causes — differ- 



THE WINDS. 



91 



ences of density caused by differences of tem- 
perature. 

d d 



I 



b 




J 



Fig, 81, Origin of Winds, 

The equilibrium of the atmosphere is disturbed 
by differences of temperature as follows : When 
any area becomes heated, as at a a, Fig. 81, the 
air over it, expanding and becoming lighter, is 
pressed upward by the colder air which rushes 
in from all sides. Thus result, the following 
currents : ascending currents, b b, over the heated 
area ; lateral, surface currents, c c, from all sides 
toward the heated area ; upper currents, d d, from 
the heated area; and descending currents, e e. 
It is the lateral currents which flow toward or 
from the heated area that are felt mainly as 
winds. The ascending currents rise until they 
reach a stratum of air of nearly the same den- 
sity as their own, and then spread laterally in 
all directions toward the areas where the air 
has been rarefied by the movements of the lat- 
eral surface currents, until they finally descend, 
and recommence their motion toward the heated 
area. These circulatory motions continue as long 
as the heated area remains warmer than surround- 
ing regions. 

In speaking of winds, reference is always made to the 
surface currents, unless otherwise stated. 

242. Origin of the Atmospheric Circulation. — 

The hottest portions of the earth are, in general, 
within the tropics; hence in the equatorial regions 
ascending currents continually prevail. To sup- 
ply the partial vacuum so created, lateral sur- 
face currents blow in toward the equator from 
the poles, while the ascending currents, after 
reaching a certain elevation, blow as upper cur- 
rents toward the poles. Thus result currents by 
which the entire mass of the atmosphere is kept in 
constant circulation, and an interchange effected 
between the air of the equator and the poles. 

The most important of these currents are the 
following : 

(1.) Polar currents, or the lateral surface cur- 



rents, which flow from the poles to the equator ; 
and 

(2.) Equatorial currents, or the upper currents, 
which flow from the equator toward the poles. 

It will be noticed that wherever the surface 
wind blows in any given direction, the upper 
wind blows in the opposite direction. 

In several instances the ashes of volcanoes have been 
carried great distances in directions opposite to that in which 
the surface wind was blowing. The smoke from tall chim- 
neys at first takes the direction of the surface wind, but 
rising, is soon carried in the opposite direction by the 
upper currents. The clouds are often seen moving in a 
direction opposite to that indicated by vanes placed on 
the tops of the houses. 

A current of air is named according to the di- 
rection from which it comes; a current of water, 
according to the direction in which it is going. 
Thus, a north-east wind comes from the north- 
east ; a north-east current of water goes toward 
the north-east. 

243. Effect of the Earth's Kotation on the 
Direction of the Wind. — Were the earth at rest, 
the equatorial and polar currents would blow due 
north and south in each hemisphere ; but by the 
rotation of the earth they are turned out of their 
course in a manner similar to the oceanic currents 
already studied. 

The polar currents, as they approach the equa- 
tor, where the axial velocity toward the east is 
greater, are left behind by the more rapidly mov- 
ing earth, and thus come, as shown in Fig. 83, 
from the north-east in the northern hemisphere, 
and from the south-east in the southern. 

The equatorial currents, under the influence of 
the earth's eastward motion, are carried toward 
the east as they approach the poles, and thus 
come, as shown in Fig. 83, from the south-west in 
the northern hemisphere, and from the north-west 
in the southern. 

Wherever the polar winds prevail, their direc- 
tion, when unaffected by local disturbances, will 
be north-east in the northern hemisphere, and south- 
east in the southern. Near the equator their di- 
rection is nearly due east. 

Wherever the equatorial currents prevail, their 
direction will be souilwwest in the northern hemi- 
sphere, and north-west in the southern. 

In Fig. 82, the equatorial currents are repre- 
sented as continuing to either pole as upper cur- 
rents, and the polar winds as surface currents to 
the equator. If this were so, constant north-east- 
erly winds would prevail in the northern hemi- 



PHYSICAL GEOGRAPHY. 



' S3 -ii-, 





Fig. 82. Direction of Wind as Affected by Rotation. Fig. 83, Interchange of the Equatorial and Polar Currents, Wind Zones. 



sphere, and constant south-easterly winds in the 
southern. Several causes, however, exist to pre- 
vent this simple circulation of the air between the 
equatorial and polar regions. 

The equatorial currents do not continue as upper 
currents all the ivay to the poles, but fall and become 
surface currents, replacing the polar winds, which 
rise and continue for a while toward the equator as 
upper currents. 

244. Causes of Interchange of Surface and 
Upper Currents. — The causes which produce this 
shifting of the equatorial and polar currents are : 

(1.) The equatorial currents become cold — 

(a.) By the cold of elevation ; 

(b.) By expansion ; 

(e.) By change of latitude. 

The equatorial currents therefore fall and are 
replaced by the polar currents, which have been 
gradually growing warmer by continuing near 
the surface of the earth. 

(2.) As the equatorial currents approach the 
poles they have a smaller area over which to 
spread, and, being thereby compressed, are caused 
to descend and become surface currents. 

This interchange between the equatorial and polar cur- 
rents takes place at about lat. 30°. It varies, however, 
with the position of the sun, moving toward the poles 
when the sun is nearly overhead, and toward the equator 
when the sun is in the other hemisphere. 

The interchange in the position of the equatorial and 
polar currents is represented in Fig. 83. 

As the equatorial currrents fall, they divide, 



part going to the poles, and part returning to the 
equator. 

The general system of the aerial circulation 
thus indicated is more regular over the oceans 
than over the land. Over the continents the 
greater heat of the land during summer causes 
a general tendency of the wind to blow toward 
the land ; similarly, the greater cold of the land 
during winter causes a tendency of the wind to 
blow toward the sea. 

245. Classification of Winds. — Winds are di- 
vided into three classes: 

(1.) Constant, or those whose direction remains 
the same throughout the year. 

(2.) Periodical, or those which, for regular pe- 
riods, blow alternately in opposite directions. 

(3.) Variable, or those which blow in any di- 
rection. 

246. Wind Zones. — The principal wind zones 
are the zone of calms, the zones of the trades, the 
zones of the calms of Cancer and Capricorn, the 
zones of the variable winds, and the zones of the 
polar winds. 

Zone of Calms. — In parts of the ocean near the 
equator the ascending currents are sufficiently 
powerful to neutralize entirely the inblowing 
polar currents, and thus produce a calm, which, 
however, is liable at any moment to be disturbed 
by powerful winds. The boundaries of the zone 
vary with the season ; they extend from about 2° 
to 11° north latitude. 






Zones of the Trades. — From the limits of the 
zone of calms to about 30° on each side of the 
equator the polar currents blow with great steadi- 
ness throughout the year. The constancy in their 
direction has caused these winds to be named 
" trade winds," from their great value to com- 
merce. Their direction is north-east in the north- 
ern hemisphere, and south-east in the southern. 

Zones of the Calms of Cancer and Capricorn. 
— Between the zones of the trades and the vari- 
ables, where the interchange takes jflace between 
the equatorial and polar currents, zones of calms 
occur. Their boundaries are not well defined, 
and are dependent on the position of the sun. 

Zones of the Variable Winds. — Beyond the 
limits of the preceding zones to near the latitude 
of the polar circles, the equatorial and polar cur- 
rents alternately prevail. Here the equatorial 
and polar currents are continually striving for 
the mastery, sometimes one and sometimes the 
other becoming the surface current. During 
these conflicts the wind may blow from any 
quarter ; but when either current is once estab- 
lished it often continues constant for some days. 
This is especially the case over the ocean, where 
the modifying influences are less marked. 

Though the winds in these zones are variable, 
still two directions predominate : south-west and 
north-east in the northern hemisphere, and north- 
west and south-east in the southern. Westerly 
winds, however, occur the most frequently in 
nearly all parts of these zones. 

The equatorial currents are sometimes called the Return 
Trades, or the Anti-trades, because they blow in the oppo- 
site direction to the trades. 

Between about lat. 25° and 40°, N. and S., over parts of 
the ocean, the winds are nearly periodical, blowing during 
the hotter portions of the year in each hemisphere from 
the poles, and during the remainder of the year from the 
equator. This zone is often called the Zone of the Sub- 
tropical winds. 

Polar Zones. — From the limits of the zones of 
the variables to the poles, there are regions of pre- 
vailing polar winds. These winds are most fre- 
quently north-east in the northern hemisphere, 
and south-east in the southern. 

247. Dove's Law of the Rotation of the Winds. — 
The equatorial and polar currents usually displace each 
other, and become surface winds in a regular order, first 
discovered by Prof. Dove of Berlin. 

In the northern hemisphere, before the polar current is 
permanently established from the north-east, the wind 
blows in Tegular order from the west, north-west, and north. 
The displacement of the polar by the equatorial currents 
occurs in the opposite direction : from the east, south-east, 



and south, before the general south-west current is perma- 
nently established. 

In the southern hemisphere these motions are reversed. 

This rotation of the winds, together with the effects 
produced on the thermometer and barometer, is indicated 
in the following diagram. Since the equatorial currents 
are warm, moist, and light, when they prevail the ther- 
mometer rises and the barometer falls. On the establish- 
ment of the polar currents, however, the thermometer 
falls and the barometer rises. 



NORTHERN HEMISPHERE. 
N. 



SOUTHERN HEMISPHERE. 

N. 




Fig. 84. Rotation of the Winds (after Dove). 

The " warm waves " of the zones of the variable 
winds are caused by the prevalence of the equa- 
torial currents. Similarly, the " cold waves " are 
caused by the prevalence of the polar currents. 

248. Land and Sea Breezes. — During the day 
the land near the coast becomes warmer than the 
sea. An ascending current, therefore, rises over 
the land, and a breeze, called the sea breeze, sets 
in from the sea. At night the land, from its 
more rapid cooling, soon becomes colder than the 
water ; the ascending current then rises from the 




Fig. 85. Land and Sea Breezes. 

water, and a breeze, called the land breeze, sets in 
from the land. The strength of these winds de- 
pends upon the difference in the temperature of 
the land and water ; they are, therefore, best de- 
fined in the tropical and extra-tropical regions, 
though they may occur in higher latitudes during 
the hottest parts of the year. Land and sea 
breezes are periodical winds. 

249. Monsoons are periodical winds, which dur- 
ing part of the year blow with great regularity in 
one direction, and during the remainder of the 



Page 94 




THE WINDS. 



95 



year in the opposite direction. They are in real- 
ity huge land and sea breezes, caused by the dif- 
ference in temperature between the warmer and 
colder halves of the year. They occur mainly in 
the regions of the trades, and are in reality trade 
winds which have been turned out of their course 
by the unequal heating of land and water. 

During winter, in either hemisphere, the oceans, 
being warmer than the land, cause a greater 
regularity in the trades; but during summer, the 
tropical continents become intensely heated, and 
their powerful ascending currents cause the equa- 
torial currents to blow toward the heated areas 
as surface winds, and thus displace the trades. 
The interval between the two monsoons is gener- 
ally characterized by calms, suddenly followed by 
furious gales, that may blow from any quarter. 

250. Monsoon Regions. — There are three well- 
marked regions of monsoons — the Indian Ocean, 
the Gulf of Guinea, and the Mexican Gulf and 
Caribbean Sea. The first is the largest and most 
distinctly marked. 

Monsoons of the Indian Ocean. — Here the 
trades are deflected by the overheating of the 
continents of Asia, Africa, and Australia. 

In the northern hemisphere the north-east trades prevail 
with great regularity over the Indian Ocean during the 
cooler half of the year : from October to April, but during 
the warmer half: from April to October, the heated Asiatic 
continent deflects the trades, and the equatorial currents 
prevail from the south-west. The same winds also pre- 
vail south of the equator, on the western border of the 
ocean, along the eastern coast of Africa as far south as 
Madagascar. 

In the southern hemisphere, in the south-eastern portion 
of the ocean, the south-east trade is similarly deflected by 
the Australian continent. Here the winds blow south- 
east during the southern winter, and north-west during 
its summer. 

Monsoons of the Gulf of Guinea. — Here the 
north-east trades are deflected by the intensely 
heated continent of Africa. The south-west sum- 
mer monsoon blows over the land as far inland 
as the Kong Mountains. 

Monsoons of the Mexican Gulf and Caribbean 
Sea. — In this region the north-east trade winds 
are deflected by the overheating of the Missis- 
sippi Valley. The Northers of Texas, which are 
cold winds blowing for a few days at a time over 
the Texan and Mexican plains, may be considered 
as connected with the winter monsoons. 

Besides the preceding well-marked regions, nearly all 
the coasts of the continents in and near the tropics have 
small monsoon regions, as, for example, the western coasts 
of Mexico, the eastern and western coasts of South Amer- 
ica, and the western and northern coasts of Africa. 



251. Desert Winds. — The rapid heating and 
cooling of deserts make them great disturbers 
of the regular system of winds. Currents al- 
ternately blow toivard and from the heated area. 
The latter are intensely hot and dry. 

The Etesian Winds. — During summer the barren 
soil of the Desert of Sahara, becoming intensely 
heated, causes strong north-east winds to blow 
over the Mediterranean Sea. These are called 
the Etesian winds, and continue from July to 
September; they are strongest during the day- 
time. 

Hot Desert Winds. — From the Sahara a period- 
ical wind, called the Harmattan, blows on the soidh- 
west, over the coasts of Guinea ; on the north, the 
Solano blows over Spain, and the Sirocco blows 
over Southern Italy and Sicily. Though some- 
what tempered during their passage across the 
Mediterranean, these winds are still exceedingly 
hot and oppressive. 

From the deserts of Nubia and Arabia in- 
tensely hot, dry Avinds blow in all directions over 
the coasts of Arabia, Nubia, Persia, and Syria. 
These winds are known under the general name 
of the simoom or samiel. From their high tem- 
perature and the absence of moisture, they often 
cause death from nervous exhaustion. 

During the prevalence of the simoom, particles of fine 
sand are carried into the atmosphere and obscure the light 
of the sun. Becoming intensely heated, these particles, 
by their radiation, increase the temperature of the air, 




Fig. 86. Sand Storm in the Desert. 



which sometimes rises as high as 120° or 130° Fahr. When 
powerful winds prevail, dense clouds of sand are carried 
about in the atmosphere, producing the so-called sand 
storms. The sand-drifts which are thus formed constantly 
change their position. 



96 



PHYSICAL GEOGRAPHY. 



The Khamsin blows at irregular intervals over 
Egypt from the south ; but when established, 
generally continues for fifty days. It is intensely 
hot and dry, like the simoom, and is loaded with 
fine sand. 

252. Mountain Winds. — During the day the 
elevated slopes of mountains heat the air over 
them hotter than at corresponding elevations over 
the valleys. Currents, therefore, ascend the val- 
leys toivard the mountains during the day. During 
the night, however, the air near the summits be- 
comes colder than that near the base. Currents, 
therefore, descend the valleys from the mountains 
during the night. 

"KJUKO" 

CHAPTER IV. 

Storms. 

253. Storms are violent disturbances of the 
ordinary equilibrium of the atmosphere by wind, 
rain, snow, hail, or thunder and lightning. 

During storms the wind varies in velocity from 
that of a scarcely perceptible breeze to upwards 
of 200 miles per hour. 

Velocity and Power of Winds. 



Velocity of Wind in 
Miles, per hour. 


Common Karnes of Winds. 


1 


Hardly Perceptible Breeze. 


4 to 5 


Gentle Wind. 


10 to 15 


Pleasant Brisk Gale. 


20 to 25 


Very Brisk. 


30 to 35 


High Wind. 


40 


Very High. 


50 


Storm. 


60 


Great Storm. 


80 


Hurricane. 


100 


Violent Hurricane. 


80 to 200 


Tornado. 



254. Cyclones are storms of considerable ex- 
tent, in which the velocity of the wind is much 
greater than usual, and the air moves in eddies or 
whirls, somewhat similar to whirlwinds, but of 
vastly greater power and diameter. 

In all such storms the wind revolves around a 
calm centre ; over the calm centre the barometer 
is low, but on the sides, and especially on that side 
toward which the storm is moving, it is high. 

Besides the rotary motion of the wind, there is 
also a progressive motion, which causes the storm 
to advance bodily, moving rapidly in a parabolic 
path. The general term Cyclone has been ap- 
plied to these storms on account of their rotary 
motion. They have also various local names. 



Cyclones originate in the tropical regions, but 
frequently extend far into the temperate zones. 




Pig, 87. A Storm at Sea. 

255. Regions of Cyclones. — The following are 
the most noted regions: 

The West Indies, where they are generally 
called hurricanes. 

The China Seas, where they are known as 
typhoons. 

The Indian Ocean. 

In each of these regions the storms occur about 
the time of the change of the regular winds, and 
have their origin in marked differences of tem- 
perature ; thus in the Indian Ocean and the China 
Seas, they generally occur at the change of the mon- 
soon, after the great heat of summer. They are at- 
tended with the condensation of moisture and in- 
tense electrical disturbance. 

256. Cause of Cyclones. — Cyclones originate in 
an area of low barometer caused by the ascending 
current of air that follows the overheating of any 
region. As the air rushes in from all sides it Ls 
deflected by the earth's rotation, and assumes a 
rotary or whirling motion around the heated area. 
The centrifugal force generated by this rotation 
causes the barometric pressure of the area to be- 
come lower and the area to grow larger. Mean- 
while the inflowing air, ascending, is chilled by 
the cold of elevation and by expansion sufficiently 
to condense its vapor rapidly. The heat energy, 
previously latent in the vapor, is now disengaged, 
and causes the air to mount higher and condense 
still more of its vapor. It is to the energy thus 
rapidly liberated by the condensation of the vapor 
that the violence of the cyclone is due. Cyclones, 
therefore, acquire extraordinary violence only 
when an abundance of vapor is present in the 
air. 



STOEMS. 



97 



As the inblowing winds come near the heated 
area, they must blow with increased violence in 
order to permit the same quantity of air to pass 
over the constantly narrowing path. 

Besides the rotary motion of the wind, the 
storm moves or progresses over a parabolic path, 
which in the tropics is generally toward the west, 
and in the temperate zones toward the east. This 
progressive motion of the storm is like the similar 



i&° N. 




Januar)- to April, 



Fig. 88. Chart showing Path and Direction of Cyclone. 

motion often noticed in a rapidly spinning top. 
It is due to the combined influences of the inrush 
of air, the earth's rotation, and centrifugal force. 
257. Peculiarities of Cyclones. — Cyclones rage 
most furiously in the neighborhood of islands and 
along the coasts of continents. They are most 
powerful near their origin. As they advance the 
spiral increases in size and the fury of the wind 
gradually diminishes, because the amount of moist- 
ure in the air is less. The rotary motion varies 



from 30 to 100 miles an hour. The progressive 
motion of the calm centre is more moderate — 
from 20 to 50 miles an hour. This progressive 
motion is least in the tropics and greatest in the 
temperate regions. 

The wind invariably rotates in the same direc- 
tion in each hemisphere ; in the northern, it ro- 
tates from right to left, or in the direction oppo- 
site to that of the hands of a watch ; in the south- 
ern, from left to right, or in the same direction as 
the hands of a watch. The cause of the regu- 



NORTHERN HEMISPHERE. 




>JS\ O) T,1\? 



SOUTHERN HEMISPHERE. 





/ 



'••--v X ( 

,.-■ ' /'HEATEOX 

Pig. 89. Cause of the Rotation of the Wind. 



Jqauol 1 



larity of rotation is seen, from an inspection of 
Fig. 89, to be due to the rotation of the earth. 
The wind, blowing in from all sides toward the 
heated area, is so deflected by the rotary motion 
of the earth as to move in vast circles, from right 
to left in the northern hemisphere, and from left 
to right in the southern. 

The force of the wind in these storms is tremendous. 
So furiously does the wind lash the water that its tem- 
perature is often sensibly raised by the friction. 

The intelligent navigator always endeavors to avoid the 
centre of the storm, since it is the most dangerous part. 
This he can do by remembering the direction of the rota- 
tion of the wind in the hemisphere he may be in ; for if, 
in the northern hemisphere, he stands so that the wind 
blows directly in his face, the calm centre is on his right, 
while in the southern hemisphere it is on his left; and in- 
stead of running with the storm, hoping to outsail it, he 
will boldly steer toward its circumference. 

258. Tornadoes and Whirlwinds are the same 
as cyclones, except that they are more limited in 
area. Their violence, however, often exceeds that 



of cyclones. Tornadoes appear to be due to ro- 
tary motion of the air occurring above the earth's 
surface, which results in a rapid sucking up of the 
warmer surface air. 

259. Water-spouts.— When tornadoes or whirl- 
winds occur on the water they cause a water-spout. 
A rapid condensation of vapor takes place, both 
from the different temperature of the winds and 
from the rarefaction produced at the centre of the 
revolving mass of air. 

Portions of the clouds are sometimes drawn 
down from above and whirled around in the 
form of an immense funnel-shaped mass ; finally 
the whirl reaches the water, and a column of 
spray is thrown up, which unites with the mass 
above and moves over the surface of the water 
as an immense pillar. Though of formidable ap- 
pearance, water-spouts have never been known 
seriously to damage large vessels. 

Similar phenomena are noticed on the land 
when tornadoes occur. Here, however, only the 
cloud cone is observed. 

260. The North-Easters and other Storms of 
the United States. — The following important facts 
have been discovered in regard to the extended 
storms which occur in the United States : 

(1.) All our great storms are attended by an 
immense whirling of the wind, and are, in fact, 
species of cyclones. 

(2.) The great north-east storms of our eastern 
sea-board usually originate in the west, in an area 
of low barometer, somewhere between Texas and 
Minnesota. In the front and rear of this area 
the barometer is high. 

(3.) The calm centre of the storm, or the area 
of low barometer, usually moves toward the north- 
east. The shape of the calm centre is longer 
from north to south than from east to west. 



(4.) The storms begin by the winds blowing 
toward the area of low barometer. 

(5.) During the prevalence of the storm the 
winds are north-east, east, or south-east ; toward 
the end, north-west, west, and south-west. 

261. Sailing Routes. — A knowledge of the di- 
rections of the winds and ocean currents has ma- 
terially diminished the time required by sailing 
vessels to go from one port to another. Opposing 
winds and currents often render it advisable for the 
vessel to begin its journey in a direction consider- 
ably out of the direct line of the desired port. 

Europe — America. — The Gulf Stream and prevailing 
westerly" winds render the passage across the ocean from 
east to west considerably longer than from west to east. 
The general route, in either direction, varies with the 
season of the year. 

New York — San Francisco. — After leaving New 
York the course is considerably to the east, in order to 
clear the South American coast in the region of the trades. 
After doubling Cape Horn the course is westward. The 
zone of the north-east trades is entered about 118° W. 
long. 

America — India — Australia. — In sailing from Amer- 
ica to India or Australia the vessel takes the same route 
as between Eastern America and San Francisco. About 
opposite Eio Janeiro, however, the routes diverge. On 
entering the Indian Ocean the direction is dependent on 
that of the prevailing monsoon. 

Europe — India — Australia. — The vessels either pass 
through the Mediterranean Sea and the Suez Canal, or 
around the Cape of Good Hope. The broad expanse of 
ocean in the southern hemisphere, in the zone of the vari- 
ables, renders the westerly winds very steady. Vessels sail- 
ing from Atlantic ports of America or Europe generally 
find it preferable to go by the eastward route, around the 
Cape of Good Hope, and return by the westward route, 
around Cape Horn, thus circumnavigating the globe. 

California — Japan. — The southerly route, from east to 
west, is aided by the north-east trades and the north equa- 
torial current of the Pacific ; the northerly route, from 
west to east, is necessary in order to avoid the trade 
winds. 

The general sailing routes between some of the most 
important ports are traced on the map of the winds. 



SYLLABUS. 



w>XKo 



Atmospheric air is composed mainly of a mixture of ni- 
trogen and oxygen, in the proportion, by weight, of about 
77 parts of nitrogen to 23 of oxygen in every hundred 
parts. The atmosphere also contains small quantities of 
carbonic acid and the vapor of water. 

The oxygen of the air is necessary to combustion and 
respiration ; the carbonic acid and the vapor of water, to 
plant-life. 

At the level of the sea the atmosphere presses on every 
square inch of the earth's surface with a force of about 15 
pounds. 



The upper limit of the atmosphere has been variously 
estimated at from 50 to 200 miles above the level of the 
sea. 

A barometer is used for measuring the pressure of the at- 
mosphere; a thermometer, for measuring its temperature. 

The vertical rays of the sun are warmer than the oblique 
rays — 1. Because they are spread over a smaller area of the 
earth. 2. Because they pass through a thinner stratum of 
air, and consequently lose less of their heat by absorption. 
3. Because they strike the earth more directly, and there- 
fore produce more heat. 



EEVIEW QUESTIONS. 



99 



Continual summer is found in the tropics ; summer and 
winter of nearly equal length in the temperate zones; 
short, hot summers, followed by intensely cold winters, in 
the polar zones. 

The atmosphere is heated — 1. Either by direct absorp- 
tion of the rays while passing through it ; or 2. By con- 
tact with, or by radiation and reflection from, the heated 
earth. 

Isothermal lines connect places whose mean temperature 
is the same. 

The mathematical zones are bounded by the parallels 
of latitude ; the physical zones, by the isotherms. 

The mathematical and physical zones do not coincide — 
1. Because of the unequal distribution of the land and 
water areas. 2. The irregularities in the surface of the 
land. 3. The distribution of the winds and moisture. 4. 
The ocean currents. 5. The difference in the rainfall. 

The temperature of the air decreases with the altitude 
— 1. Because the air receives most of its heat from the 
earth's surface, so that it must grow continually colder the 
farther we go above the surface. 2. The decreased den- 
sity and humidity of the air prevent it from absorbing 
either the direct rays of the sun or those reflected or ra- 
diated from the earth. 

Places situated near the sea have a more equable, uni- 
form climate than those in the same latitude in the inte- 
rior of the continent. 

Whenever any part of the earth's surface is heated more 
than the neighboring parts, ascending currents occur over 
the heated area, lateral surface currents blow in toward 
the heated area, and upper currents blow from the heated 
area. 

The general system of the atmospheric circulation con- 
sists mainly of the following currents : 1. The polar cur- 
rents, blowing from the poles toward the equator. 2. The 
equatorial currents, blowing from the equator toward the 
poles. 

The direction of these currents is modified by the rota- 
tion of the earth. Thus modified, the equatorial currents 
are south-west in the northern hemisphere, and north- 
west in the southern. The polar currents are north-east 
in the northern hemisphere, and south-east in the south- 
ern. 



When a wind at the surface blows in any direction, there 
is generally an upper current blowing in the opposite di- 
rection. 

The equatorial currents do not continue as upper cur- 
rents to the poles — 1. Because they become cooled and fall. 
2. From the contracted space of the higher latitudes when 
compared with that of the equator. 

We distinguish the following wind zones : the zone of 
calms ; the zones of the trades ; the zones of the calms of 
Cancer and Capricorn; the zones of the variables; and the 
zones of the polar winds. 

Land and sea breezes are caused by the unequal heating 
of the land and water during day and night ; monsoons, 
by their unequal heating during summer and winter. 

Monsoons occur on the coasts of tropical countries within 
the limits of the trade zones. They are most frequent in 
the Indian Ocean, in the Gulf of Guinea, and in the Mex- 
ican Gulf and neighborhood. 

The Etesian Winds blow over the Mediterranean toward 
the Desert of Sahara. 

The Hot Winds caused by the deserts of Sahara and 
Arabia are the Harmattan, over Guinea; the Solano, over 
Spain ; the Sirocco, over Italy ; the Simoom, over Arabia, 
Nubia, and Persia; and the Khamsin, over Egypt. 

In most mountainous regions winds blow up the valleys 
toward the mountains during the day, and down the val- 
leys from the mountains during the night. 

Cyclones are caused by the wind blowing in from all 
sides toward an area of low barometer caused by the 
overheating of the area. The centrifugal force thus gen- 
erated increases both the size of the area and the differ- 
ence of pressure as compared with regions surrounding 
it. The fury of the storm is increased by the heat energy 
liberated by the condensation of the vapor in the uprush- 
ing air. 

Storms occur whenever the ordinary equilibrium of the 
atmosphere is violently disturbed by wind, rain, snow, 
hail, or thunder and lightning. 

Nearly all powerful storms are attended with a rotation 
of the wind. Such storms are known under the general 
names of Cyclones, Hurricaues, Typhoons, and Tornadoes. 

The north-easters and other great storms of the United 
States are species of cyclones. 



REVIEW QUESTIONS. 



Of what use is the atmosphere in the economy of the earth ? 

Define meteorology. 

Describe the construction of a barometer. 

What proof have we that the greater part of the atmo- 
sphere, by weight, lies within a few miles of the earth's 
surface ? 

Define hypsometry. 

Describe the construction of a thermometer. 

Why are the vertical rays of the sun warmer than the 
oblique rays? 

What is the characteristic climate of the tropics? Of 
the temperate regions? Of the polar regions? 

In what different ways does the atmosphere receive its 
heat from the sun ? 

State the boundaries of the mathematical torrid zone. 
Of the physical torrid zone. Of the mathematical and 
physical temperate zones. Of the mathematical and phys- 
ical frigid zones. 
12 



In what parts of the eastern hemisphere is the greatest 
mean annual temperature found? In what parts of the 
western hemisphere? 

What influence is produced on the climate of high lati- 
tudes by a preponderance of moderately elevated land 
masses? On the climate of the tropics? 

Why should the temperature of the atmosphere decrease 
with the altitude ? 

Name all the causes which prevent the mathematical 
climatic zones from coinciding with the physical climatic 
zones. 

What is the origin of winds? 

Name the currents of which the atmospheric circulation 
principally consists. 

Explain the action of the rotation of the earth on the 
direction of the equatorial and polar currents. 

Name the causes which produce the shifting of the equa- 
torial and polar currents. 



100 



PHYSICAL GEOGRAPHY. 



Name the principal wind zones of the earth. 

Explain, in full, the origin of land and sea breezes. In 
what respect do monsoons resemble land and sea breezes? 

Name the principal monsoon regions of the earth. 

Describe the origin of desert winds? 

Name the winds which are caused by the desert of Sa- 
hara. By the deserts of Arabia and Nubia. 

What are storms ? 

What are cyclones? Where do they originate? In 
>vhat direction does the wind rotate in the northern 



hemisphere? In the southern hemisphere? In what di- 
rection does the storm progress in each hemisphere? Ex- 
plain the cause of the rotation of the wind. 

What are hurricanes ? Typhoons? 

Explain the formation of a water-spout. 

Is the water in the upper part of a water-spout salt or 
fresh ? 

Name the important facts which have been discovered 
respecting the north-easters and other severe storms of the 
United States. 



MAP QUESTIONS. 



-»o>*;o 



Trace on the map of isothermal lines the areas of great- 
est heat in the eastern hemisphere. In the western hemi- 
sphere. 

Show from the map of the isothermal lines wherein 
the physical torrid zone differs in position from the 
mathematical torrid zone. 

In which hemisphere do the isothermal lines deviate 
more from the parallels of latitude, in the northern or 
the southern? 

Trace on the map of the isothermal lines the limit of 
the Arctic drift ice. Of the Antarctic drift ice. 

What are the mean summer and winter temperatures 
of Sitka? Of Quebec? 

What causes exist to render the climate of Sitka so 
much warmer than that of Quebec, notwithstanding the 
difference of their latitudes? 

What are the mean summer and winter temperatures of 
Mexico, Madras, Singapore, Berlin, London, Philadelphia, 
Algiers, Melbourne, and Eio Janeiro? 

What instances can you find on the map of the in- 
crease in the mean annual temperature of places through 



the influence of ocean currents? Of winds? Of rain- 
fall? 

Name similar instances of places whose mean annual 
temperature is lowered by such causes. 

Trace ou the map of the winds the boundaries of the 
various wind zones. State the direction of the wind in 
each of these zones. 

Poiut out the limits of the monsoon regious of the 
world. 

What hot winds blow over Arabia? Over Egypt? Over 
Greece and Italy ? Over Guinea? 

What cold wind blows over Texas? 

Describe the path of the West India hurricanes. How 
far to the north do these storms extend ? 

Describe the path of the Mauritius hurricanes. Where 
do these storms originate ? How far to the south do they 
extend ? 

Describe the region of the typhoons. 

Describe the route a vessel would take in sailing from 
America to Europe. From New York to San Francisco. 
From America to Australia. 




PRECIPITATION OF MOISTURE. 



101 



Section II 



MOISTURE OF THE ATMOSPHERE. 



-~*9<o 



CHAPTER I. 

Precipitation of Moisture. 

262. Evaporation. — From every water surface, 
and even from masses of ice and snow, there is 
constantly arising, at all temperatures, an invisible 
vapor of water. Water vapor is about three-fifths 
as heavy as air. It diffuses readily through the 
air, and is borne by the winds to all parts of the 
earth. This giving off of vapor from the surface 
of water is called evaporation. It is evaporation 
which dries the wet earth, when the moisture is 
unable either to pass off the earth's surface by 
drainage, or to soak through the porous strata. 

About one-half, by weight, of the vapor of the atmo- 
sphere is within a little over a mile above the mean sea 
level. 

263. The Rapidity of Evaporation is influ- 
enced by the following circumstances: 

(1.) The temperature of the atmosphere. The 
capacity of the air for absorbing moisture in- 
creases with an increase of temperature. Warm 
air can retain more vapor than cold air. 

(2.) The extent of surface exposed. Evapora- 
tion takes place only from the surface ; therefore, 
the greater the surface, the greater the evapora- 
tion. 

(3.) The quantity of vapor already in the air. 
Dry air absorbs moisture more rapidly than moist 
air. All evaporation ceases when the air is com- 
pletely saturated. 

(4.) The renewal of the air. During very calm 
weather, the air in contact with a water surface 
becomes saturated, and so prevents further evapo- 
ration. Gentle breezes, by renewing the air, in- 
crease the rapidity of evaporation. 

(5.) Pressure on the surface. A diminished 
atmospheric pressure increases the rapidity of 
evaporation. 

264. The Dew Point. — When the air contains 
as much vapor as it is capable of holding, it is 
said to be at its dew point. 

The quantity of moisture necessary to saturate a given 
quantity of air and bring it to the dew point, varies with 



the temperature. Cold air requires less moisture to satu- 
rate it than air which is warmer, and, therefore, may feel 
damper than warm air, which may contain more vapor. 
We thus distinguish between the actual humidity, or the 
amount actually present in a given volume of air, and 
the relative humidity, or the relation between the amount 
present and that required to saturate the air at the given 
temperature. 

The humidity of the air is determined by means of an 
instrument called a hygrometer. 

Weight in grains of aqueous vapor in one cubic foot of 
saturated air at different temperatures. (Silliman.) 



Temperature, Fahr. 


Weight in Grains. 


Approximate Values. 


0° 


0.545 


0.6 


10° 


0.841 


0.9 


20° 


1.298 


1.3 


30° 


1.969 


2.0 


40° ' 


2.862 


2.9 


50° 


4.089 


4.1 


60° 


5.756 


5.8 


70° 


7.992 


8.0 


80° 


10.949 


11.0 


90° 


14.810 


15.0 


100° 


19.790 


20.0 



No matter how much aqueous vapor a given 
quantity of air contains, if its temperature be 
lowered, it will grow relatively moister until, if the 
fall of temperature be sufficient, its dew point is 
reached; and as soon as the temperature falls 
below the dew point, a deposition of moisture 
will begin, either in the liquid or solid state. 

265. Precipitations. — The invisible vapor may 
be precipitated from the atmosphere and become 
visible, either as dew, mist, fog, cloud, rain, sleet, 
hail, or snow. These are called precipitations. 

Law of Precipitations. 

In order that any precipitation may occur, the 
air must be cooled below the temperature of its dew 
point. 

266. Distribution of Precipitations. — The quan- 
tity of moisture in the air depends on its tempera- 
ture, and its vicinity to the sea. 

The amount of precipitation regularly decreases 
as we pass from the equator to the poles, and from 
the coasts of the continents toward the interior. 

267. Dew. — If, during a warm day, a dry glass 
be filled with cold water, the outside of the glass 
will soon become covered with small drops of 
water, derived entirely from the air. The air 



102 



PHYSICAL GEOGRAPHY. 



which comes in contact with the cool sides of the 
glass has its temperature lowered below the dew 
point, and deposits as vapor the moisture it no 
longer can retain. 

The dew which is deposited during certain sea- 
sons of the year on plants and other objects on 
the earth, has a similar origin. Objects on the 
earth cool more rapidly than the surrounding air, 
which deposits its moisture on them whenever 
they lower its temperature below the dew point. 
When the objects are colder than 32° Fahr., the 
dew is deposited as hoar-frost. 

Dew falls or is deposited more heavily on some 
objects than on others ; this is because some ob- 
jects radiate or give off their heat more rapidly 
than others, and thus becoming cooler, they con- 
dense more of the moisture of the air. 

More deiv is deposited during a clear night than 
during a cloudy one, because objects cool more rap- 
idly when the sky is clear than when it is cloudy. 

Thick clothing keeps the body warm, not because the 
clothes give any heat to the body, but because they are non- 
conductors, and prevent the escape of heat from the body. 
In like manner the clouds, acting as blankets to the earth, 
prevent its losing heat rapidly. 

More dew falls or is deposited during a still night 
than during a windy one. 

The air must remain long enough in contact 
with cold objects to enable them to lower its tem- 
perature and collect its moisture. Powerful winds 
prevent this, while gentle breezes favor the depo- 
sition, by bringing fresh masses of air into contact 
with the cold objects. 

In the tropics, during seasons when the sky is clear, the 
dew is so copious that it resembles a gentle rain. 

In the deposition of dew, the moisture is derived from a 
comparatively thin stratum of air in the immediate neigh- 
borhood of the cool object. All other kinds of precipita- 
tions are produced by the cooling of a large mass of air. 

268. Fogs and Clouds. — Whenever the tem- 
perature of a large mass of air is reduced below 
its dew point, its moisture begins to collect in 
minute drops, which diminish the transparency 
of the air, and form fogs or mists, when near the 
surface, and clouds, when in the upper regions of 
the atmosphere. Fogs and clouds are the same in 
their origin and composition, and differ only in 
their elevation. 

The minute drops of water that form clouds 
and fogs, though formed of a substance about 
eight hundred times heavier than air, are pre- 
vented from settling rapidly by the resistance of 
the air. This is rendered possible by the minute 



size of the drops, which are much smaller than 
the relatively heavier dust-particles, which are 
wafted about by the winds. Whenever the drops 
exceed a certain size, they fall as rain or snow. 

It was once believed that the moisture in fogs and clouds 
existed in the form of hollow babbles or vesicles, filled 
with air, and that the clouds or fogs ascended, whenever 
the contained air expanded the bubbles and rendered 
them specifically lighter. This idea is now generally 
abandoned. 

Clouds or fogs result whenever a mass of air is 
cooled below the temperature of its dew point, 
as, for example, when two bodies of air of dif- 
ferent temperatures are mingled, especially if, 
as is generally the case, the warmer of the two 
is the moister. On the contrary, clouds or fogs 
disappear on the approach of a dry, warm wind. 
Clouds are higher in the tropics than in the polar 
regions, and generally are higher during the day 
than during the night. 

Off the banks of Newfoundland, the warm, moist air of 
the Gulf Stream is cooled by the cold, moist air of the 
Labrador ocean current. Hence result the dense fogs so 
frequent over this part of the ocean. 

269. Classification of Clouds. — Clouds assume 
such a variety of shapes, that it is difficult to 
classify them. Meteorologists, however, have rec- 
ognized the existence of four primary forms : the 
cirrus, the cumulus, the stratus, and the nimbus. 




Fig. 90. Primary Forms of Clouds, 
■v- Cirrus. -v- -v Cumulus. 

The Cirrus Cloud consists of fleecy, feathery 
masses of condensed vapor, deposited in the 
higher regions of the atmosphere. The name 
cirrus is derived from the resemblance the cloud 
bears to a lock of hair. These clouds are called 



PRECIPITATION OF MOISTURE. 



103 



by sailors cats' tails or mares' tails. From their 
elevation, the moisture is, probably, generally in 
the condition of ice-particles. Halos, or circular 
bands of light around the sun, are caused by light 
passing through cirrus clouds. 

The Cumulus, or Heap Cloud, is a denser cloud 
than the cirrus, and is formed in the lower re- 
gions of the air, where the quantity of vapor is 
greater. Cumulus clouds generally consist of 
rounded masses, in the shape of irregular heaps, 
with moderately flat bases. They are caused by 
ascending currents of air, which have their moist- 
ure condensed by the cold produced by expan- 
sion and elevation. Cumulus clouds occur dur- 
ing the hottest part of the day. Their height 
seldom exceeds two miles. 




Pig, 91. Primary Porms of Clouds. 
■v Nimbus, -v -v Stratus. 

The Nimbus, or Storm Cloud, is any cloud from 
which rain falls. Any of the various forms of 
clouds may collect and form a nimbus cloud. 
The nimbus is not considered as a distinct form 
of cloud by some meteorologists. 

The Stratus, or Layer Clouds, form in long, 
horizontal sheets or bands. These clouds are 
most common in the early morning and evening, 
when the ascending currents are weak. They 
j.re caused by the gradual settling of cumulus 
and other clouds. The stratus is the lowest form 
of cloud ; it sometimes falls to the surface of the 
earth, and becomes a fog. 

The cirrus, stratus, and cumulus clouds assume 
a variety of shapes, producing various secondary 
forms. 

270. Secondary Forms of Clouds. — The cirro- 
stratus, the cirro-cumulus, and the cumulo-stratus 



are the most prominent secondary forms of 
clouds. The first two are modifications of the 
cirrus cloud ; the latter, of the cumulus. 




Fig. 92. Secondary Forms of Clouds. 
-»-Cirro-Cumulus. -v -v-cirro-Stratus. -»--v-«-Cumulo-Stratus. 

The Cirro-Cumulus is a cirrus cloud, arranged 
in little rounded masses, shaped something like 
cumuli. They are sometimes called " wool sacks," 
and indicate dry weather. 

The Cirro-Stratus is a cirrus cloud which has 
settled in bands or layers. The bands are not 
continuous, but are arranged in blotches or bars, 
and often give to the sky the speckled appear- 
ance of a mackerel's back, producing the so-called 
mackerel sky. 

The appearance of a mackerel sky indicates — 1. That 
the moisture of the upper strata of air is condensing; 2. 
That it is growing dense enough to arrange itself in 
layers. Therefore, a mackerel sky generally indicates 
approaching rain. 

The Cumulo-Stratus is the form produced by 
the heaping together of a mountain-like mass of 
cumulus clouds ; the base partakes of the nature 
of the stratus cloud, but the top clearly resembles 
cumuli. These clouds differ but little from the 
nimbus, or storm cloud. 

271. Rain. — When, during the formation of a 
cloud, the condensation of moisture continues, the 
drops of which the cloud is composed increase 
in size, and, uniting, fall to the earth as rain. 
Rain which freezes while falling forms sleet. As 



104 



PHYSICAL GEOGRAPHY. 



the drops fall through the cloud they grow larger 
by the addition of other drops which unite with 
them. Raindrops, therefore, are larger when the 
clouds are thicker. They are, in general, larger 
in the tropics than in the polar regions, and dur- 
ing the day than at night. 

To produce rain, it is necessary that the tem- 
perature of a large mass of air be .reduced con- 
siderably below its dew point. There are several 
ways in which this cooling may be effected : 

(1.) By a change of latitude. A warm, moist- 
ure-laden wind may blow into a cold region. The 
equatorial currents of air deposit their moisture 
in the temperate and polar zones on account of 
the chilling experienced as they recede from the 
equator. 

(2.) By a change of altitude. By an ascending 
current of air, which carries the moisture of the 
lower strata into the upper regions, where the 
cold there existing, together with that produced 
by the rapid expansion of both air and vapor 
under the diminished 'pressure, condenses the moist- 
ure of the air. It is mainly in this manner that 
the rains of the tropical regions are caused. 

The rain in mountainous districts has a similar 
cause. A moist wind, reaching a mountain-range, 
is forced by the wind back of it to ascend the 
slopes. Contact with the cold, upper slopes causes 
condensation of the vapor as rain. 

(3.) The mingling of masses of cold and warm 
ah: By this means heavy clouds and a moderate 
rainfall may be produced ; but the precipitation 
can never be considerable, because the cooler air 
will be warmed by the mixing, and, therefore, 
will have its capacity for moisture increased in- 
stead of diminished. 

272. Distribution of the Eainfall.— The dis- 
tribution of rain may be considered both as re- 
gards its periodicity and its quantity. The distri- 
bution of the rain is dependent upon the direction 
of the winds. Each wind zone has a character- 
istic rainfall. 

The following simple principles determine the 
rainfall in any particular wind zone : 

(1.) The equatorial currents are rain-bearing, 
because they are moist, and while on their way 
to the poles, their temperature and consequent 
capacity for moisture, is constantly decreasing. 

(2.) The polar currents are dry, because they 
are constantly increasing in temperature as they 
approach the equator ; hence they take in, rather 
than give out, moisture. 



When they have reached the zones of the trade winds, 
the polar currents may bring abundant rains, provided 
they have previously crossed an ocean. They then dis- 
charge the moisture with which they are saturated, either 
by an ascending current, or by blowing against the ele- 
vations of the continent. 

273. Periodical Rain Zones. 

The Zone of Calms. — In the zone of calms it 
rains nearly every day. In the early morning 
the sky is cloudless ; but near the middle of the 
day, as the heat increases, the ascending currents, 
rising higher, begin to condense their moisture ; 
cumuli clouds form, and, increasing rapidly, soon 
cover the sky, when torrents of rain descend, ac- 
companied by thunder and lightning. After a 
few hours the rain ceases, and the sky again be- 
comes clear. In this zone it seldom rains at 
night. 

274. The Zone of the Trades. — Since the trades 
are generally dry winds, it is only when their tem- 
perature is considerably decreased that they can 
cause rain. In the zone of the trades, except in 
mountainous districts and on the windward coasts 
of a continent, the rainfall occurs during the 
greatest heat of the season, when the sun is di- 
rectly overhead and the ascending currents are 
powerful. Hence, it rains during a few months 
in summer, when immense quantities of water 
fall ; the remainder of the year is dry. Copious 
dews, however, occur at night. 

The precipitation is not continuous throughout the en- 
tire summer. Since the rain only falls when the sun is 
nearly overhead, a brief interval of dry weather occurs 
in regions near the equator, thus dividing the season into 
two parts : one, during the passage of the sun over the 
zenith; the other, on his return to the zenith from the 
adjacent tropic. Near the limits of the zone, however, the 
two seasons are merged into one. 

Over the ocean, during most of the year, there 

is no rain in the zone of the trades, although the 

actual humidity of the air is quite high. 

Between latitude 24° and 30°, in both the Northern and 
Southern Hemispheres, there are regions of comparatively 
scanty rains. Here the summers are not hot enough to 
cause rain by the ascending currents, but are sufficiently 
hot to prevent the equatorial current from bringing much 
rain. Here also the return branch of the equatorial cur- 
rent becomes drier on its return to the equator. 

275. The Monsoon Region of the Indian Ocean.- 
During the prevalence of the winter monsoon, the north- 
east winds bathe the eastern shores of Hindostan in copious 
rains, while the western shores, shielded by the ranges of 
the Ghauts, are dry. During the summer monsoon, the 
south-west wiuds bathe the western shores and the south- 
ern slopes of the Himalayas in heavy rains, while the 
eastern shores are dry. This monsoon also brings rains to 
the western coasts of the peninsula of Indo-China. 



PRECIPITATION OF MOISTURE. 



105 



276. Non-Periodical Rain Zones. 

The Zones of the Variable Winds. — In these 
zones rain may occur at any season of the year, 
and at any hour of the day or night. Here it 
is the equatorial currents which bring the rain. 
These regions are sometimes called the zones of 
perennial rains, or of constant precipitation. In 
the greater part of these zones, the equatorial 
currents are more frequent in summer than in 
winter. The rainfall is, therefore, greatest dur- 
ing summer. 

Rainfall in the Zone of the Polar Winds. — In 
these zones the winters are dry, because the dry, 
cold polar currents then prevail ; but during the 
summer the equatorial currents sometimes pre- 
vail, and bring with them dense clouds and fogs, 
accompanied by drizzling rains. The snows occur 
mainly in spring and autumn. 

277. Quantity of Rain. — The quantity of rain 
which falls in a given time on any area is deter- 
mined by means of an instrument called the rain- 
gauge or pluviometer. 

The rain-gauge is generally constructed in the form of 
a cylindrical vessel with a horizontal base, surmounted 
by a funnel-shaped top. A vertical glass tube communi- 
cates with the bottom of the vessel from the outside, 
and allows the water to mount in it to the same height 
as that in the inside. The rain-gauge is placed in an ex- 
posed position, where it is free from eddies or whirls. 
If, during any given time, the water in the instrument 
is one inch deep, then during that time the rainfall over 
the area equals one inch. In speaking of the rainfall of 
a country, the moisture which may fall as snow is always 
included. 

An inch of rain over a surface a square yard 
in area equals in weight 461 pounds : on the sur- 
face of an acre, it is nearly equal in weight to 
100 tons. 

The annual rainfall is distributed, as regards 
quantity, as follows : 

Irrespective of the elevations of the surface, 
more rain falls in the tropics than in the temperate 
regions, and more in the temperate than in the 
polar regions. The quantity thus decreases with 
moderate regularity from the equator toward the 



poles. This is caused by a similar decrease in the 
quantities of heat and evaporation. 

While the amount of rain that falls decreases from the 
equator to the poles, the number of cloudy or rainy days 
increases, being greater at the poles than at the equator. 

More rain falls on the coasts of a continent than 
in the interior, since near the ocean the winds are 
moister. That coast of a continent which first 
receives the prevailing wind has the greatest 
rainfall. 

More rainfalls in the Northern Hemisphere than 
in the Southern. This is due to the greater extent 
of the land-area of the Northern Hemisphere. 

Mountains receive a heavier rainfall than the 
plains below, because the moist winds, in order 
to cross the mountains, are forced to ascend their 
slopes and thus pass into a colder region of the 
atmosphere. Therefore, the sources of rivers are 
generally found in mountainous districts. Moun- 
tains are among the most important causes of rain. 

When the mountains are high, the winds may 
reach the opposite slopes dry and vaporless. The 
tropical Andes of South America afford an excel- 
lent example of this. 

Plateaus, though higher than plains, receive, as 
a rule, less rain, because they are generally sur- 
rounded by mountain chains, which rob the winds 
of their moisture. Moreover, the air over a pla- 
teau is warmer than at a corresponding height in 
the atmosphere, and therefore dissolves, rather 
than condenses, the moisture. 

The rainfall of the New World, both in the 
tropical and temperate regions, is greater than 
that of the Old ; thus, in the tropics of the New 
World, 115 inches of rain fall yearly, while the 
same portions of the Old World receive but 77 
inches. In the temperate zones in America the 
annual rainfall is 39 inches, while in Europe it 
is but 34 inches. 

The mean annual rainfall at Philadelphia, according to 
Prof. Kirkpatrick, is 46.93 inches. The figures are based 
on observations during 16 consecutive years. 

The preceding principles find ample illustration in the 
following tables : 



Table of Annual Rainfall (H. K. Johnston). 
Rainfall in the Tropics. 



OLD WORLD. 

IncheB. 

Ceylon 91.7 

Hindostan, mean of the Peninsula 117.5 

Sierra Leone, Guinea 189.6 

Macao, China 68.3 

Canton 69.2 



NEW WOELD. 

Inches. 

San Luis de Maranhao, Brazil 280.00 

Cayenne, Guiana. 116.27 

Paramaribo, Guiana. 229.20 

Grenada, Lesser Antilles 103.41 

Havana, Cuba 90.66 



106 



PHYSICAL GEOGRAPHY. 



Rainfall in the Temperate Zone. 



Inches. 

Madeira 29.82 

Sicily 23.55 

W. side of Apennines.. 35.17 
E. " " ..26.70 

S. " Alps 57.57 

N. " " 35.27 



Inches. 

Southern France 23.54 

Southern Germany 26.64 

Netherlands 26.70 

British Islands, Plain..27.00 

" " Mts.... 50.00 

W. Coast Scandinavia..82.12 



Mean Eainfall in Europe in the Temperate 

Zone 34 inches. 



AMERICA. 

Inches. 

Key West, Florida 35.26 

Charleston, S. C 47.60 

Washington, D. C 36.30 

Marietta, Ohio 34.16 

West Chester, Penna : 46.89 

Cambridge, Mass 38.42 

Burlington, Vt 39.44 

Eastport, Maine 36.28 

New York 36.28 

Mean Bainfall in the United States in the 
Temperate Zone 39 inches. 



610 ins. 



600 ins. 
500 " 
400 " 
300 " 
200 " 
100 " 



301 ins. 



" ~ 


^m 


167 ins. 














^^m 


— ■ l - 


W=^ 


107.6 ins. 




















82 ins. 




































46.9 ins. 








^= 


jsm 


— —^ 


^H 


^^ 




38 ins. 


32 ins. 


7 ins. 


Cherrapon- 


Mahabuleah 


Vera 


St. Do- 


Bergen, 


Philadelphia, 


Cambridge, 


British 


Alexandria, 


gi, India. 


war, India. 


Cruz. 


mingo. 


Norway. 


Penna. 


Mass. 


Isles. 


Egypt. 



Fig, 93. Comparative Rainfall. (The figures represent the annual rainfall in inches.) 



278. Rainless Districts. — In some parts of the 
world, rain is either entirely absent, or falls only 
in limited quantities, at long intervals. The most 
extensive rainless districts are found in the east- 
ern continent. 

Desert Belt of the Eastern Continent. — From 
the western shores of Northern Africa eastward 
to the Great Kinghan Mountains in Asia, extends 
an almost uninterrupted belt of desert lands. It 
includes the great desert of the Sahara, the Ara- 
bian and Persian Deserts, and the Desert of Mon- 
golia. The aridity is most absolute in the west, 
where, in the Sahara and in the desert of Arabia, 
rain seldom, if ever, falls. Toward the east, in 
Persia and Mongolia, scanty rains occur, but the 
country has the appearance of a desert. 

The cause of this immense desert tract is to be 
found in the dry trade winds, which blow over 
most of the region. Having previously crossed 
the vast continent of Asia as upper currents, they 
arrive at the deserts dry and vaporless. Even 
that portion of the region which receives the 
winds from the Mediterranean has no rainfall, 
because any clouds that may form, are soon dis- 
sipated by the hot air of the desert. 

Persia and Mongolia owe their deserts to their 



high mountain borders, which rob the clouds of 
their moisture before they cross the interior pla- 
teaus. The high system of the Himalayas effect- 
ually prevents any of the moisture of the south- 
west currents from penetrating the plateau of 
Mongolia. 

Arid tracts occur in the Kalahari desert, in Africa, and 
near the tropic of Capricorn, in Australia. 

Desert Belt of the Western Continent. — The 

desert lands of the Western Continent are more 
contracted in area. In North America, the largest 
desert is in the Great Interior Plateau. Here the 
mountain borders, especially the Sierra Nevada 
on the west, deprive the interior of rain. The 
aridity is not absolute, since scanty rains occur 
over parts of the region. Portions of the penin 
sula of California and of the Mexican Plateau 
also resemble deserts. 

In South America, on the western slopes of the 
Andes, between the parallels of 27° and 23° S., 
is found the desert of Atacama. Here rain never 
falls, although the ground is occasionally refreshed 
by mists and dews. The cause of the absence of 
rain is to be traced to the high Andes, which con- 
dense all the moisture of the trades on their east- 



HAIL, SNOW, AND GLACIEES. 



107 



em slopes, the winds thus arriving dry and va- 
porless at the western. 

Cause . of Deserts. — Deserts are caused entirely 
by the absence of moisture. Their soil, though gen- 
erally finely pulverized, or sand-like, does not dif- 
fer, save in the absence of vegetable mould, from 
that of other areas. Thus neither the nature of 
its temperature, nor its soil, is the cause of the 
desert of Sahara, since a vigorous vegetation al- 
ways follows the appearance of water, on the suc- 
cessful boring of an artesian well. It is probably 
true that deserts, once formed, tend to perpetuate 
themselves, by the influence their naked surfaces 
exert on the rainfall. 



o*;o 



CHAPTER II. 

Hail, Snow, and Glaciers. 

279. Hail falls when considerable differences 
of temperature exist between higher and lower 
strata of air, and the moisture is suddenly con- 
densed in the presence of great cold. Generally, 
several layers or bands of dark, grayish clouds 
are seen. Hail falls most frequently in summer, 
near the close of an excessively warm day. 

Structure of the Hailstone. — If a large hailstone be 
placed on a hot surface until one-half is melted, the struc- 
ture can be readily examined. Concentric layers, similar 
to those of an onion, will he noticed, arranged around a 
central nucleus, sometimes of ice and sometimes of snow, 
though generally the latter. The stones are more or less 
oblately spheroidal in shape. Their general weight varies 
from a few grains to several ounces, but they have been 
known to weigh several pounds. 



in rapid succession into the two clouds, thus receiving al- 
ternate coatings of ice and snow, until at last they are 
hurled to the ground. 





Fig. 94. Structure of a Hailstone. 

Origin of Hail. — The cause of hail is not ex- 
actly understood, and several theories have been 
framed to account for it. One of these is the 
Rotary Theory. 

The wind is supposed to rotate as in a cyclone, only the 
axis of the whirl is horizontal instead of vertical. ■ Two 
horizontal layers of cloud exist — the upper layer of snow, 
the lower, of rain. The snowflakes, which form the nu- 
clei of the hailstones, are caught in the whirl, and dipped 
13 



Fig. 95. Eotary Theory of Hail. 

Thunder and lightning are the invariable attendants of 
hailstorms, and some authorities have attributed the for- 
mation of the stones to successive electrical attractions 
and repulsions of the snowflakes between a snow and a 
rain cloud. Others have imagined a number of alternate 
layers of snow and rain, and have attributed the hail- 
stones to drops of rain falling through the successive 
clouds. 

280. Snow. — When the moisture of the air is 
condensed at any temperature below 32° Fahr., 
the vapor crystallizes, and snowflakes are formed. 

The snowflakes grow, as they fall, by condensing addi- 
tional moisture from the air. They are larger in mild 
than in cold weather. 

Snow-crystals assume quite a variety of forms, but are 
built up by various groupings of minute rhombohedrons 
of ice. The star-shape is the most common. 




Fig. 96. Snow-Crystals. 

If the temperature of the air near the surface 
is much warmer than 32° Fahr., any snow that 
is formed in the upper regions will melt before 
reaching the ground. Hence, in the temperate 
zones, as a rule, snow falls only in winter, while 
in the tropics it never falls, except near the sum- 
mits of lofty mountains. 

It is a mistake to suppose that the fall of snow is greater 
in regions near the poles than elsewhere; for in high lati- 



108 



PHYSICAL GEOGRAPHY. 



tudes there is comparatively little moisture in the air. 
The fall is heaviest in the cool temperate regions. 

281. Snow Line. — Kegions of Perpetual Snow. 

— The snow which falls on mountains is slowly 
pressed down the slopes by the weight of the 
snow above. The distance it will move down the 
mountain before melting depends on a number 
of circumstances. The lower limit of the line is 
called the snow line, above which are the regions 
of perpetual snow, in which the ground is covered 
with snow throughout the year. 

The height of the snow line depends — 

(1.) On the amount of the snoiufall. The greater 
the fall, the farther down the mountain the snow 
will move before melting. 

(2.) On the temperature of the valley. The 
warmer the valley the higher the snow line. 
The snow line is, therefore, highest in the trop- 
ical regions, and lowest near the poles. 

(3.) On the inclination of the mountain slope. 
The steeper the slope, the more rapidly the snow 
will move, and the farther it will go before melt- 
ing, therefore, the lower the snow line. 

According to Guyot, the snow line, subject to variations, 
is about three miles above the sea in the tropics ; rather 
less than two miles in the temperate latitudes ; and less 
than a mile near the northern extremities of the conti- 
nents ; while still farther north, on the polar islands, the 
snow line is but a few hundred feet above the sea. Over 
the polar oceans, the winter snows are but partially melted, 
and help to produce the huge ice-floes of these regions. 

SNOW LINE. 

Europe.— Norway, lat. 70° N 3,400 feet. 

" " 60° N 5,500 " 

Alps, lat. 46° N. (south side) 9,200 " 

" " " " (north side) 8,800 " 

Asia.— Altai Mountains, lat. 50° N 7,000 " 

" Himalayas, lat. 31° N 17,000 " 

Africa.— Kilimandjaro, lat. 3° S 16,000 " 

North America. — Eocky Mountains, lat. 

43° N 12,467 " 

South America. — Andes, Ecuador, lat. 1° S. 15,800 " 

" " ". lat. 54° S 3,700 " 

The snow line is generally lower in a moist atmosphere 
than in dry air, because of the greater fall of snow in the 
former case than in the latter. As a rule, that slope of a 
range which is exposed to the prevalent wind has a lower snow 
line than the opposite slope. The position the slope occupies 
in relation to the vertical rays of the sun, also exerts an 
influence on the height of the snow line. 

282 Glaciers are immense masses of ice and 
snow, which move almost imperceptibly down the 
higher mountain valleys or slopes. Their upper 
parts are formed of soft snow ; their lower por- 
tions of clear, hard ice. Their origin is as fol- 
lows : The weight of the huge snow fields, which 



form above the snow line, presses the mass slowly 
down the slopes. The pressure, due to the weight 
of the layers, but especially the pressure which is 
produced when the mass is forced through a con- 
traction in the valley, squeezes out the confined 
air, to which snow, in great part, owes its white 
color, and the lower part of the glacier thus be- 
comes changed into a compact mass of pure ice. 
The alternate thawing and freezing to which the 
mass is subjected below the snow line, also con- 
tribute to the change from snow to ice. 

The change is most thorough in the lower parts of the 
glacier, where the ice is marvellously clear. Its color, 
when seen in great depths, is of a deep azure blue ; in the 
middle portions of the glacier the ice is coarse and white. 
The higher region of but partially changed snow is called 
the neve region. Here the snow occurs in coarse white 
grains. The process of formation is a continuous one. 
The nev6 region is supplied by fresh falls of snow, which 
replace those pressed down the slopes. 

283. Drainage of Snow and Ice. — Glaciers 
closely resemble rivers, since they receive the 
drainage of their basins through the solid mate- 
rial which flows into them ; their motion, how- 
ever, is much slower. Like rivers, they have 
their tributaries, and their peculiarities of flow 
and velocity. 

Several glaciers often unite and flow on as one 
mass ; but their solid condition prevents the in- 
termingling which occurs in rivers, and the sepa- 
rate streams can generally be distinctly traced 
throughout the remainder of their course. Like 
rivers, the top and middle portions move more 
rapidly than the sides or bottom, owing to the 
diminished friction. 

284. Peculiarities of Glaciers. — The surface 
of the glacier is often comparatively smooth ; but 
when irregularities occur, either in the direction 
of the valley, or in the slope of its bed, the glacier 
is broken into deep fissures, called crevasses. These 
are most numerous on the sides, from which they 
extend either obliquely up the stream, or directly 
across, in deep transverse fissures. The former 
are generally due to a bend in the valley, one 
side being compressed and the other extended; 
the latter, to steep and abrupt descents in the bed. 
Orevasses are, therefore, rapids in the ice stream. 

Crevasses vary in breadth from mere crevices, that a 
knife-blade can scarcely penetrate, to yawning chasms 
over 100 feet in width. The depth of the wider crevasses 
is generally profound. Their vertical walls afford a con- 
venient opportunity for studying many peculiarities of 
formation. Looking down the walls of the crevasses, the 
ice appears of a deep azure blue. The surface ice is a dirty 
white. 



HAIL, SNOW, AND GLACIERS. 



109 



The crevasses gradually disappear below the cause of 
disturbance, the fractures rejoining by a process called 
regelation. Eegelation is the property which fragments of 
moist ice have of becoming firmly cemented together, when 
their surfaces are brought into contact under pressure. 

The water derived from the melting of the ice 
issues from a cavernous arch at the end of the 
glacier. The volume of the issuing stream, which 
is often considerable, is dependent on the tempera- 
ture, being greater during the warm months of 
the year. Many rivers have their origin in these 
glacier streams ; as, the Rhone and the Rhine, in 
Europe, and the Ganges, in Asia. 

The distance the glacier extends below the snow 
line depends on the mass and velocity of the ice, 
and the rapidity with which it is melted. When 
the winter snows are light, and the following sum- 
mer unusually warm, the end of the glacier re- 
treats up the mountain. On the contrary, heavy 
snowfalls in winter, followed by a cool summer, 
permit the end of the glacier to advance far into 
the valley below. 

285. Transporting Power of Glaciers. — All 
along the borders of the valleys, stones and dirt 
roll down the declivities, and, accumulating on 
the surface of the moving mass, are carried with 
it to a lower level. These accumulations of dirt 
and stones are called moraines; they are most 
sharply marked at the sides of the glaciers, where 
they are called lateral moraines. Where two gla- 
ciers flow into one common valley a moraine called 
the medial moraine marks the junction of their 
meeting edges. At the end of the glacier, a ter- 
minal moraine extends in a wide curve across the 
valley. Medial moraines are sometimes over a 
hundred feet in height. Terminal moraines some- 
times attain the height of several hundred feet. 

The masses of stone transported by glaciers are often of 
great size. Some have been found 100 feet long, 50 feet 
wide, and 40 feet high. 

286. Erosion. — Such immense masses of ice 
must deepen considerably the valleys through 
which they move. When they have deserted 
their former valleys, evidences of their previous 
existence are to be found in the long lines of 
unstratified rocks and mud left by their moraines 
and boulders, and especially in the deep grooves, 
or scratches, cut in the bottom or sides of the 
valleys by rocks imbedded in the moving ice 
mass. These scratches are parallel, and show 
the direction of the motion. 

The water which issues from the terminal cave is deeply 
charged with a fine sediment, the result of erosion. This 



sediment is exceedingly fertile, and, spread out by the 
rivers on the flood-grounds, becomes a source of agricul- 
tural wealth. 

Fiords and Glacial Lakes. — Valleys cut by 
glaciers are characterized by parallel sides. Gla- 
cial valleys, when formed on mountains that slope 
down to the ocean, if the region is subjected to 
subsequent depression and the valleys partially 
submerged, are penetrated by the sea, and form 
arms of the sea extending far into the mountains. 
Such valleys are called fiords. 

The following are the most important fiord 
regions : 

(1.) On the coasts of Norway. 

(2.) On the western coasts of the Dominion of 
Canada and Alaska. 

(3.) On the coasts of Greenland, where the 
valleys are still covered with ice masses. 

The numerous lakes of glacial regions owe their 
origin either to the erosion of softer rocks, or to 
the damming up of rivers by the terminal mo- 
raines left by a retreating glacier. 

287. Geographical Distribution of Glaciers. — 
The best known glacial system in the world is 
found in Europe, in the region of the Central 
Alps. Here no less than 1100 glaciers are found, 
one hundred of which are of large size. 

One of the best known of the European glaciers is that 
of the iter de Glace (Sea of Ice). It descends from the 
slopes of the range of Mont Blanc, and is formed by the 
confluence of three large glaciers: the Glacier du Geant, the 
Glacier de Lechaud, and the Glacier du Talefre. 




Fig, 97. The Mer de Glace, 

Glaciers occur also in the Pyrenees Mountains ; in the 
Caucasus range; and in the Scandinavian plateau, from 
which they descend into the Norwegian fiords to less than 
1000 feet from the level of the sea. They also occur in the 
Patagonian Andes 



110 



PHYSICAL GEOGRAPHY. 



In the Arctic zone glaciers are particularly 
numerous and extensive. Here they generally 
reach down into the sea. They are found in the 
islands of the Arctic Archipelago, in Greenland, 
Iceland, Jan Mayen, and Spitzbergen. 

The Humboldt Glacier, in Greenland, is sixty-nine miles 
broad at its lower extremity in the sea. In all the Arctic 
glaciers, the neve region is more extended than in those 
of more southern latitudes. The terminal moraines are 
found at the bottom of the sea, near the foot of the 
glacier. 

In the lofty mountain-ranges of the Himalayas and in 
the Karakorum, occur other less known, though exten- 
sive, regions of glaciers. 

288. Icebergs. — When the glacier extends into 
the sea, the base is undermined by the warmer 
waters of the ocean, and great fragments are 
broken off by the waves, forming floating moun- 
tains of ice, called icebergs. Icebergs are particu- 
larly numerous in the North Atlantic, into which 
they descend from the extensive Arctic glacial 
region already described. 

The limits of the Arctic and Antarctic drift ice are 
shown in the map of the isotherms. 




Fig. 98, Icebergs. 

The ice floes of the polar seas have their origin 
in the snow which falls into the cold water, re- 
maining partially dissolved and subsequently 
freezing, thus adding to the thickness of the ice 
formed. 



289. The Glacial Epoch of the Earth.— Toward the 
close of the Mammalian Age, a change occurred in the cli- 
mate of the earth, and extensive glaciers covered most of 
the northern continents, reaching, in many instances, far 
toward the south. In the United States, their southern 
limit appears to have been at about lat. 39° N., in Southern 
Pennsylvania, Ohio, Indiana, Illinois, and Iowa. In Eu- 
rope, they extended as far south as the 50° N. lat. In 
South America, they probably extended as far toward the 
equator as 41° S. lat. 

The evidences of the existence of ancient glaciers are 
found in the presence of accumulations of unstratified 
material, called the drift; in the presence of old moraines; 
in glacial scratches and grooves on rocky slopes ; in eroded 
valleys; and in the presence of numerous large boulders, 
which are found at great distances from their places of 
origin. 



oXXo 



CHAPTER III. 

Electrical and Optical Phenomena. 

290. Nature of Electricity. — Electricity is now 
generally believed to be due to a peculiar wave 
motion in the luminiferous ether, the medium 
which transmits the waves of light and heat. 

When a body is electrified it acquires a certain 
power of doing work, called electric potential. 
Electric potential is measured in units called 
volts. The path through which an electric dis- 
charge passes is called the circuit. All circuits 
offer a measurable resistance to the passage of an 
electric discharge. Electric resistance is meas- 
ured in units called ohms. 

The rate at which electricity passes through a 
circuit is called the current, and is measured in 
units called amperes. An ampere is the current 
which would pass in a circuit whose resistance is 
one ohm, under a potential of one volt. 

Though electricity is probably not a fluid, yet it resem- 
bles a fluid in many respects, and the units already re- 
ferred to are, to a certain extent, based on this resem- 
blance. The quantity of liquid that flows through a pipe 
in a given time depends on the pressure on the liquid, and 
the resistance offered by the pipe. The quantity-per-sec- 
ond corresponds to the amperes ; the pressure which causes 
the flow, to the volts ; and the resistance which limits the 
flow, to the ohms. 

Electricity may be produced in bodies by a 
variety of causes : such as friction, heat, chemical 
action, magnetism., and animal or vegetable life. 

There are two distinct forms of electrical excitement: 
the positive and the negative. A body with a high potential 
is generally assumed to be positively charged ; one with a 
low potential, negatively charged. The current is assumed 
to flow from the higher to the lower potential, or from the 
positive to the negative. Bodies charged with electricity 



ELECTRICAL AND OPTICAL PHENOMENA. 



Ill 



of the same kind, repel one another ; if charged with dif- 
ferent kinds, they attract, and if the bodies are free to 
move, they approach, when the opposite excitements neu- 
tralize each other. In case the electrical excitement is 
considerable, the union is accompanied by a sharp crack, 
and a flash of light, called the electric sparlc. 

291. Conductors of electricity are bodies which 
allow its ready passage through them. Metals, 
charcoal, acids, aqueous solutions, and various 
animal and vegetable substances, are good con- 
ductors. Non-conductors are those which do not 
allow the electricity to flow freely through them. 
Gums, resins, glass, silk, and dry air are non-con- 
ductors. > 

The higher the conducting power of a circuit the lower 
will be its resistance, and, consequently, the greater the 
current which will be sent through it by a given poten- 
tial. 

292. Atmospheric Electricity. — Electric excite- 
ment is always present in the atmosphere. The 
electricity of the air is generally positive, although 
it often changes rapidly to negative on the ap- 
proach of clouds or fogs. It is feeblest within a 
few feet of the surface, and increases with the 
elevation above the general surface of the earth. 

Origin of Free Atmospheric Electricity. — The elec- 
tricity of the atmosphere is caused by a variety of circum- 
stances, the chief of which are evaporation and condensa- 
tion ; unequal heating of the earth by the sun's rays ; 
combustion; animal and vegetable life; and the friction 
of winds against each other or against the earth's sur- 
face. 

293. Lightning occurs when the electricity of 
a cloud discharges to the earth or to a neighbor- 
ing cloud. The discharge is attended by a vivid 
spark, called lightning. The destructive effects 
of lightning are due to the discharge between the 
clouds and the earth. 

Thunder. — The heat of the spark vaporizes the 
rain-drops, and enormously expands the air, pro- 
ducing, on their subsequent cooling, a partial 
vacuum, which is further increased by the mo- 
mentary pushing aside of the air by the discharge. 
The surrounding air rushing violently into this 
vacuum produces the sound called thunder. 

The potential of the lightning flash is enormously higher 
than that produced by artificial means, and must be equal 
to many millions of volts. This high potential is due to 
the enormous decrease in the surface of a single rain-drop 
from the thousands of smaller drops which have coalesced 
to form it. 

294. Varieties of Lightning-. — There are five varieties 
of lightning : zig-zag or chain, sheet, heat, globular, and vol- 
canic lightning. 

Zig-zag Lightning probably owes its forked shape to 
the resistance which the air offers to its passage through 



it. The air-particles, being crowded together in the path 
of the spark, the lightning darts to one side, where the air 
is less dense. 

Sheet Lightning generally accompanies thunder- 
storms, and appears as an expanded flash, which illu- 
mines the clouds. 

Heat Lightning, or lightning without thunder, is gener- 
ally seen near the horizon, during hot weather. It is 
probably caused by the reflection of lightning from a 
storm below the horizon. 

Globular Lightning. On rare occasions, the lightning- 
appears in the form of a globe of light, which remains 
stationary in the air or moves slowly through it. Its 
cause is unknown. 

Volcanic Lightning. During the eruption of volca- 
noes, vivid flashes of lightning often occur in the air near 
the craters. Volcanic lightning is probably caused by the 
rapid condensation of the vast volumes of vapor emitted 
with the ashes and lava. 

295. Lightning Eods, invented by Franklin, 
protect the buildings on which they are placed, by 
quietly discharging the electricity from the over- 
hanging cloud. They generally effect this by an 
opposite electricity passing from the earth up the 
rod, and neutralizing that of the cloud. Unless 
the rods are placed in good metallic connection 
with the earth, and with all conductors near 
them, they are sources of danger rather than of 
protection. 

296. St. Elmo's Eire. — When the atmosphere 
is highly charged with electricity, faint tongues 
of fire are often seen on the ends of bodies in 




Fig, 99. St. Elmo's Fire. 

connection with the earth, like the masts of ships, 
steeples, etc., due to an electric discharge, known 
as the brush-discharge. They are called St. Elmo's 
fire, and are harmless. 



112 



PHYSICAL GEOGRAPHY. 



297. The Aurora Borealis, or northern light, 
is a phenomenon of marvellous beauty, occurring 
in the sky of high latitudes in both the northern 
and southern hemispheres. It appears in a va- 
riety of forms ; at times huge pillars of fire move 
rapidly across the heavens, or the entire northern 
sky is lighted as by a drifting storm of luminous 
snow. The commonest apj^earance, however, is 
that of an arch of fire, from which streamers 
flash toward the zenith. 

Auroras are most frequent in high latitudes, 
though not in the immediate vicinity of the 
poles. 

Auroras are caused by the passage of electricity through 
the rare air of the upper regions. The proofs are as fol- 
lows: During the continuance of an aurora, the telegraph 
wires show the presence of an unusual electrical disturb- 
ance, and the magnetic needle is subject to frequent oscil- 
lations; moreover, the same phenomena can be produced 
by the passage of an electrical current through rarefied 
gases, as in the Geissler tubes — different colors arising 
from its passage through different gases. 




Fig. 100. Aurora Borealis, 

298. Magnetism. — The recent researches of 
Herz leave little doubt that electro-magnetic phe- 
nomena are due to a wave motion in the lurni- 
niferous ether. 

Magnets are bodies which have the power of 
attracting particles of iron or the opjDosite poles 
of other magnets. 

All magnets possess an atmosphere of influence 
surrounding them, called the magnetic field. The 
magnetic field is traversed by lines of force, which 
come out of the magnet at one point and enter it 
at another, thus forming a magnetic circuit. The 



points where the lines come out are called poles ; 
the former being the positive or north pole, and 
the latter the negative or south pole. 

Magnets are either natural or artificial. Nat- 
ural magnets are found in lodestone, a species of 
iron ore composed of oxygen and iron. Pieces 
of hardened iron or steel may be magnetized, by 
rubbing them with a lodestone, or by passing 
electrical currents around them, thus forming 
what are called electro-magnets. All magnetiz- 
able substances become magnetized when they 
are brought into a magnetic field. 

If a magnetized bar or needle be suspended at 
its centre of gravity so as to move freely in a 
horizontal plane, after a few oscillations it will 
come to rest, Avith one of its ends pointing nearly 
to the geographical north pole of the earth. This 
end of the magnet is called its north pole, the op- 
posite end its south pole, and the magnet itself, a 
magnetic needle. 




Fig. 101. The Magnetio Keedle. 

299. Magnetic Attractions and Repulsions. — If a 
magnet is brought near a magnetic needle, attraction oi 
repulsion will ensue — repulsion, when the poles are of the 
same name; attraction, when they are of opposite names. 
Thus, when a north pole is approached to a north pole, or 
a south pole to a south pole, they repel each other ; but 
when a north pole is approached to a south pole, or a south 
pole to a north pole, they attract. If the approaching 
magnet is powerful, it will deflect the magnetic needle, 
although several feet distant from it ; and if placed per- 
manently in this position, the magnetic needle will no 
lonyer point to the north, hut will turn toward the disturbing 
magnet. 

300. The Magnetic Properties of the Earth.— 
The Magnetic Needle.— The magnetic, needle 
points to the north for the same reason that the 
opposite poles of magnets point to each other 
when they are sufficiently near. The entire earth 
acts as one huge magnet, ivith its poles in the neigh- 
borhood of the extremities of its axis, and the mag- 
netic needle points toward these poles on account 
of their attraction. 



ELECTRICAL AND OPTICAL PHENOMENA. 



113 



The earth, like all magnets, possesses a magnetic field. 
Lines of magnetic force come out of its north pole, pass 
around the earth through the air, and enter the earth at 
its south pole. A magnetic needle, placed in the earth's 
field, if free to move, will come to rest with the earth's 
lines of force passing into its south pole and passing out of 
its north pole. That pole of the needle which points to 
the geographical north is, therefore, of opposite magnetic 
polarity to the earth's polarity in the Northern Hemi- 
sphere. In the United States, the Northern Hemisphere 
is regarded as possessing south magnetic polarity; in 
France, as possessing north magnetic polarity. 

301, Origin of the Earth's Magnetism. — The 
exact cause of the earth's magnetism is unknown. 
Currents of electricity circulating around a con- 
ductor render it a magnet. Electrical currents 



are generated in nearly all substances, when they 
are unequally heated. The earth appears to owe 
its magnetism to the circulation around it of cur- 
rents of electricity, produced, most probably, by 
the unequal heating of different portions of its 
surface by the sun's rays. These currents would 
follow the sun in its apparent motion from east 
to west. Since the earth's magnetism appears to 
have its remote cause in the sun's heat, variations 
in the temperature should be followed by corre- 
sponding variations in the intensity of magnetism. 
This is found to be the case. 

Magnetic storms, or unusual variations in 
the earth's magnetism, have been noticed to 




Fig. 102, Declination Chart. 
(West Declination is represented by the continuous lines ; East Declination by the dotted lines ; the Agones by the heavy lines.) 



correspond with outbursts of solar activity, as 
manifested by the unusual occurrence of new 
spots. 

302. Variations in the Manifestations of Mag- 
netic Properties. — The earth's magnetic poles do 
not correspond with its geographical poles. The 
magnetic needle, therefore, except in a few local- 
ities, does not point to the true geographical north, 
but to the east or to the west of it This deviation 
from the true north is called the declination or vari- 
ation, and is east or ivest according as the needle 
points to the east or the west of the true or geo- 
graphical north. The amount of this variation 
differs in different parts of the earth. 



The position of the magnetic poles of the earth is not 
always the same, but changes slowly from year to year, 
thus producing corresponding changes in the declination 
of the needle. This change is called secular variation. The 
needle, at any place, points more and more to the east, 
following the change of the poles. At length, after a long 
period, it becomes stationary, and then begins to move 
toward the true meridian, which it at length reaches ; 
when, continuing its motion, the declination becomes 
west. 

Isogonal Lines. — Lines connecting places which 
have the same declination, are called isogonal lines. 
Lines connecting these places, when the needle 
points to the true north, are called agones, or lines 
of no declination. 

The direction of the isogonal lines is shown in the de- 



114 



PHYSICAL GEOGRAPHY. 



clination chart, the figures near the lines giving the value 
of the declination in degrees. The agone in each hemi- 
sphere is marked 0. In the New World it enters South 
America near Eio Janeiro, curves to the eastward around 
the Antilles, passes near Washington, through the western 
part of Hudson Bay, and enters the magnetic pole at 
Boothia Felix. The agone, in the Old World, passes 
through the west of Australia, near the western coasts 
of Hindostan, through Persia, the eastern part of the Cas- 
pian Sea, and through the White Sea, in Europe. The 
oval curves in Eastern Asia seem to indicate a secondary 
magnetic pole. 

In nearly all Europe, in the whole of Africa and Arabia, 
in eastern North and South America, and in nearly all the 
Atlantic and Indian Oceans, the declination is west. It is 
also west along part of the eastern shores of Asia, around 
the secondary magnetic pole. In the remainder of the 
world the declination is east. 

303. The Inclination or Dip of the Needle. — 
The lines of force of the earth's magnetic field 
are in most places inclined to the earth's surface. 
The position of the needle is, therefore, horizontal 
in but a few localities. In most places, one of the 
poles is inclined to the earth. This is called the 
inclination or dip of the needle. In the Northern 
Hemisphere, it is the north pole, and in the south- 
ern, the south pole that is inclined. 

304. Magnetic Equator. — The angle of dip is 
greater, the nearer we approach either magnetic 
pole. At the pole, the needle points vertically 
downward ; midway between the poles, the needle 
is horizontal ; the last position is called the mag- 
netic equator. 

Lines connecting places which have the same angle of 
dip are called isoclinal lines. They correspond in a very 
remarkable manner with the isothermal lines. This seems 
to show the dependence of the intensity of magnetism on 
the distribution of the sun's heat. The inclination is also 
subject to secular changes, like the declination. 

305. Optical Phenomena are caused by changes 
in the direction, intensity, or composition of sun- 
light during its passage through the atmosphere. 

Sunlight, when passed through a prism, is dis- 
persed or separated into a great number of differ- 
ent colored lights. The following seven groups of 
colors are prominent : violet, indigo, blue, green, 
yellow, orange, and red. These are called the pris- 
matic colors, or, collectively, a spectrum. They 
differ in the ease with which they are refracted, 
or turned out of their course, in passing from 
one medium to another of different density. The 
above prismatic colors seen in the spectrum are 
named in the order of their refrangibility, begin- 
ning with the violet, the most refrangible, and 
ending with the red, the least refrangible. 

306. Rainbows are arches of the prismatic 
colors, caused by the dispersion of the light 



during its passage through the falling drops of 
rain. The rays entering the drop, are reflected 
from the surfaces farthest from the sun, and 
emerge separated into the prismatic colors. 

Rainbows are seen when the observer stands 
with his back toward the sun. They are largest 
when the sun is nearly setting. 

A secondary bow sometimes occurs outside the 
primary, with the order of its colors reversed. 
It is caused by the light which is twice reflected 
from the back of the drops. 

307. The Sunset Tints of the Sky are yellow, 
orange, and red. The rays of the setting sun are 
dispersed, during their passage through the clouds, 
or through accumulations of vapor at the horizon, 
and only the colors that are least turned out of 
their course, the yellow, the orange, and the red, 
pass through and light up the western sky. 

308. The Blue Color of the Sky is caused by 
the diffusion through the" air and their subsequent 
reflection from its particles of the more refrangi- 
ble rays of light : the indigo and the blue. 

309. Halos and Coronse are rings of prismatic 
colors surrounding the sun and moon. 

Halos are caused by the presence in the air 
of small crystals of ice or snow. Parhelia, or 
mock suns, and Paraselenes, or mock moons 
(bright spots which somewhat resemble suns and 
moons), are frequently seen where the complicated 
circles of halos intersect each other. Coronce are 
circles of light, seen most frequently around the 
moon. They are caused by the presence of a 
small quantity of condensed vapor in the air. 
They generally indicate changes in the weather. 




Pig. 103. Halo. 

310. The Mirage is a general term applied to 
the appearance which objects present when viewed 
by means of rays of light that have passed through 



SYLLABUS. 



115 



strata of air, which gradually increase or decrease 
in density. In this way the objects appear either 
inverted or erect, but always out of their true 
position. Sometimes the objects are repeated, one 
being seen above the other. The mirage occurs 
both over water and land. It is caused by the 
turning of the rays of light out of their original 
direction. 

The Mirage of the Desert occurs over hot, arid 
surfaces, wheneve'r the strata of air increase rap- 
idly in density from the surface upward. The 
rays of light from distant objects, such as trees, 
are reflected from one of the lower layers of air, 



and, entering the eye of the observer, appear to 
come from inverted objects, which seem to be 
surrounded by a sheet of water. The image of 
a real tree is seen, but out of its true situation, so 
that when the observer reaches the place he finds 
nothing. 

The mirage frequently occurs on the sea. Ves- 
sels that are too far below the horizon to be di- 
rectly visible, become visible by refraction. This 
phenomenon is called looming. The vessels are 
seen both erect and inverted, and sometimes ap- 
pear suspended in the clouds. Distant islands 
are sometimes visible from the same cause. 



SYLLABUS. 



-»o>©4o 



The rapidity of evaporation increases — 1. With the tem- 
perature of the atmosphere. 2. With the extent of sur- 
face exposed. 3. With a decrease in the quantity of va- 
por already in the air. 4. With the renewal of the air ; 
and, 5. With a decrease of the pressure on the surface. 

When air can hold no more moisture in an invisible 
state, it is said to be saturated or at its dew point. 

Whenever the air is lowered below the temperature of 
its dew point, its moisture is deposited as cloud, mist, 
snow, hail, sleet, or rain. 

More dew is deposited on clear nights, when the wind is 
moderate, than on cloudy nights, when the wind is high. 

In fogs, mists, and clouds, the moisture is condensed as 
minute drops. 

Clouds owe their variety of forms to the action of aerial 
currents, and their constant tendency to settle. 

The dense fogs so common off the banks of Newfound- 
land are caused by the chilling of the warm, moist air of 
the Gulf Stream by the cooler air of the Labrador cur- 
rent. 

The primary forms of clouds, are the cirrus, the cumu- 
lus, the nimbus, and the stratus. 

The secondary forms of clouds, are the cirro-stratus, the 
cirro-cumulus, and the cumulo-stratus. 

Eain falls whenever the temperature of a mass of air is 
lowered considerably below the temperature of its dew 
point. 

This reduction of temperature may occur — 1. By a 
change of altitude by means of ascending currents. 2. 
By a change of latitude, as by the warm equatorial cur- 
rents flowing into colder regions nearer the poles. 3. A 
comparatively small rainfall may be caused by the inter- 
mingling of moist cold and moist warm air. 

As a rule, the equatorial currents bring rain, the polar 
currents, drought. 

In the zone of calms, it rains during the hottest part of 
the day, or in the afternoon, when the ascending currents 
are strongest. 

In the zone of the trades, it rains during the hottest 
part of the year, or in summer. 
14 



Between lat. 24° and 30°, both N. and S., the rainfall is 
scanty, and in some localities almost absent. 

In the zone of the variables, it may rain at any hour of 
the day or night, or at any time of the year. 

In the polar zones, the winters are clear; snows and 
drizzling rains occur in spring and autumn. 

Between lat. 30° and 35°, both N. and S., it is dry in 
summer during the prevalence of the polar currents. The 
rest of the year is wet. 

The rainfall of any place is determined by means of an 
instrument called a rain-gauge or pluviometer. 

An inch of rain on the surface of a square yard is equal 
in weight to 46.75 pounds ; an inch on the surfaee of an 
acre, to the weight of about 100 tons. 

The quantity of rain decreases from the equator to the 
poles, and from the coasts of the continents toward the 
interior. 

More rain falls on mountains than on plains ; more on 
plains than on plateaus; more in the Northern Hemi- 
sphere than in the Southern. 

In the tropics of the New World, the annual rainfall is 
115 inches ; in the Old World, only 77 inches. 

In the temperate regions of the New World, the annual 
rainfall is 35 inches ; in the Old World, but 34 inches. 

The average rainfall of Europe, between lat. 36° and 60° 
N., is 34 inches. 

The average rainfall in the United States, between 24° 
30' and 45° north latitude, is 39 inches. 

The desert belt of the eastern continent extends from 
the western shores of Northern Africa eastward to the 
Great Kinghan Mountains in Asia. It includes the Sa- 
hara, the Arabian and Persian Deserts, and the Desert of 
Mongolia. The aridity of this immense tract is caused by 
the absence of rain. 

The desert tracts near the summits of high mountains 
are caused by the absence of heat and liquid moisture. 

Hail falls when bodies of warm and intensely cold air 
are rapidly commingled. 

Snow falls when the moisture is condensed at tempera- 
tures at or below 32° Fahr., under conditions favorable to 



116 



PHYSICAL GEOGRAPHY. 



gradual crystallization while the moisture is condensing. 
Sleet is frozen rain. 

The snow line is the distance above the sea where snow 
remains throughout the year. 

The suow line in the tropics is found at about three 
miles above the level of the sea ; in the temperate regions, 
at rather less than two miles ; near the northern extremi- 
ties of the continents, at less than one mile ; while still 
farther north, on the polar islands, it is but a few hundred 
feet above the sea. 

The height of the snow line, depends — 

(1.) On the amount of the snowfall. 

(2.) On the temperature of the valley. 

(3.) On the inclination of the slopes. 

Glaciers are immense masses of ice, formed by the snow 
which accumulates on the slopes of mountains above the 
snow line. They move slowly by gravity down the moun- 
tain slopes, bearing with them accumulations of dirt and 
stones, called moraines. 

The upper surface of the glacier is generally broken into 
deep fissures, called crevasses. 

The water derived from the melting of the glacier issues 
in a stream from the lower end of the ice mass. It is 
highly charged with sediment derived from the erosion 
of the glacier. It often forms the source of a powerful 
river. 

The following mountains contain glaciers : the Alps, the 
Pyrenees, the Caucasus, the Scandinavian Mountains, the 
Himalayas, and the Karakorum. 

When glaciers descend into the sea, the waters under- 
mine them, and detach huge masses, which float away to 
great distances. These masses are called icebergs. 

Toward the close of the Mammalian Age, a change oc- 
curred in the climate of the earth, by which all the north- 
ern continents were covered with glaciers. 

The unit of electric potential is called a volt ; the unit 
of current is called an ampere; the unit of resistance is 
called an ohvi. 

Comparing the flow of electricity to that of a current 
of water in a pipe, the volt corresponds to the pressure 
causing the flow, the ohm to the friction or other resist- 



ance opposing it, and the ampere to the quantity of the 
flow per second. 

The free electricity of the air is generally positive. 

Lightning results when the electricity of a cloud dis- 
charges to the earth, or to a neighboring cloud. 

There are five kinds of lightning: zig-zag, heat, sheet, 
globular, and volcanic. 

When the air contains au unusually great quantity of 
electricity, faintly luminous balls are seen on the ends of 
tall objects. These are called St. Elmo's fire. 

Auroras are caused by the passage of electricity through 
the rare air of the upper regions of the atmosphere. 

The earth acts like a huge magnet. It possesses a mag- 
netic field, and has lines of force entering its south pole 
in the Northern Hemisphere, and coming out of its north 
pole in the Southern Hemisphere. 

A magnetic needle, if free to move, will come to rest in 
the earth's field with the lines of force of the earth pass- 
ing in at its south pole and coming out at its north pole. 

The magnetic needle points to the north, from the action 
of the magnetic poles of the earth. The cause of the 
earth's magnetism is not certainly known. It is probably 
due to electrical currents which circulate around it. 

Magnetic storms, or unusual variations in the earth's 
magnetism, correspond with outbursts of solar activity 
as manifested by sun-spots. 

The deviation of the needle from the true north, is 
called its declination; the deviation from a horizontal 
plane, its inclination. Both declination and inclination 
are subject to diurnal, annual, and secular variations. 

Isogonal lines connect places which have the same dec- 
lination. Isoclinal lines connect places which have the 
same inclination. Isoclinal lines are nearly coincident 
with the isothermal lines. 

Rainbows are caused by the action of light on falling 
raindrops. 

Halos are caused by snow crystals in the air ; Coronse, by 
minute particles of water. 

The Mirage is caused by the bending of the rays of light 
from their original direction, while passing from one me- 
dium to another of different density. 



REVIEW QUESTIONS. 



-ooXKo 



What do you understand by evaporation ? 

Name the circumstances upon which the rapidity of 
evaporation depends. 

Define dew point. 

What condition is necessary in order that the invisible 
moisture of the atmosphere may become visible in any 
form of precipitation ? 

Under what circumstances is dew deposited ? 

Why is more dew deposited on a clear night than on 
a cloudy night? Why is more dew deposited on a still 
night than on a windy one? 

Under what circumstances are fogs, or mists, produced ? 
How do fogs or mists differ from clouds ? 

What is the condition of the particles of water which 
form the clouds? Are they minute drops, or hollow vesi- 
cles? 

Describe the appearance of the cirrus cloud. How does 
its height compare with that of other clouds ? 

During what parts of the day are stratus clouds most 
common ? To what do they owe their banded appearance ? 



Describe the cumulus cloud. During what part of the 
day is it most common? 

Why should the cirro-stratus clouds generally indicate 
approaching rain ? 

Name three conditions under which rain may be caused. 
By which are the heaviest rains geuerally produced? 

Are the equatorial currents likely to bring rain or 
drought? The polar currents? Why? 

Name the periodical rain zones. 

When does it rain in the zone of calms? In the zone 
of the trade winds? Why? 

In what portions of the zone of the variable winds is 
the rainfall approximately periodical? 

Describe the rainfall in the zone of the variable winds. 
In the zone of the polar winds. 

Describe the construction of a rain-gauge or pluvi- 
ometer. 

Why should more rain fall on a mountain than on tho 
lowlands at its base? Why should more rain fall on the 
coasts of a continent than in the interior? 



REVIEW AND MAP QUESTIONS. 



117 



Compare the mean annual rainfall of the tropics of the 
Old and New Worlds. Of the temperate regions of the 
Old and New Worlds. 

Name the rainless districts of the Eastern Continent. 
Of the Western Continent. 

What is the cause of the almost total absence of j-ain in 
these districts ? 

Under what circumstances is hail produced ? 

Describe the structure of a hailstone. 

Explain the rotary theory of hail. 

Define the snow line. Upon what does the height of 
the snow line depend? At what height above the sea- 
level is it found in the tropics? In the temperate re- 
gions? In the polar zones? 

How are glaciers formed? In what respects do they 
resemble rivers? 

What are crevasses? How are they formed ? 

Name some rivers which take their origin in the melt- 
ing of glacial ice. 

Define lateral moraines; medial moraines; terminal 
moraines. 

Explain the manner in which fiord-valleys were 
formed. What is the probable origin of lakes in all 
glacier districts? 

Name some of the European mountain systems which 
contain extended glacier regions. Name two Asiatic 
mountain ranges which contain such regions. 



How are icebergs formed ? Is the ice of which they are 
composed salt or fresh ? 

What are ice floes ? State their origin. 

What appears to have been the southern limit of the 
glaciers in the United States, during the glacial epoch, 
which occurred toward the close of the Mammalian Age? 

What is the origin of free atmospheric electricity ? 

Define volt ; ohm ; ampere ; potential ; circuit. 

Under what circumstances does lightning occur? What 
is the cause of the accompanying thunder? 

Name five varieties of lightning. 

By what are auroras caused ? 

What is the cause of the directive tendency of the mag- 
netic needle ? 

What is believed to be the cause of the earth's magnet- 
ism? 

What do you understand by the earth's magnetic field ? 

Define isogonal lines; isoclinal lines. 

With what lines are the isoclinal lines nearly coinci- 
dent? 

Explain the phenomenon of the rainbow. 

What is the cause of the sunset tints of the sky ? Of 
the blue color of the sky? 

What are halos and coronfe ? By what are they caused ? 

Explain the cause of the mirage of the desert. 

What do you understand by the phenomena of loom- 
ing? 



MAP QUESTIONS. 



-«j>*;o 



Trace on the map of the winds and rains, the portions 
of the world included in the zone of calms. When does 
it rain in the zone of calms ? 

Trace in a similar manner the portions included in 
the zones of the trades, and the zones of the variables. 
What is characteristic of the rainfall in each of these 
zones ? 

Why should the eastern shores of tropical South Amer- 
ica be moist, and the western dry? 

To what peculiarity of position does Northern Africa 
owe its scanty rainfall ? 



Trace on the map of the isothermal lines the southern 
limit of the Arctic drift ice; the northern limit of the 
Antarctic drift ice. 

Trace on the declination chart, the agone, or line of no 
declination, in the Western Hemisphere. 

Trace the line of no declination in the Eastern Hemi- 
sphere. What smaller line of no declination exists in this 
hemisphere ? 

Notice that in the Western Hemisphere the isogonal 
lines all meet in a point near Hudson Bay. What does 
this meeting indicate? 




Part V. 



PLANT LIFE, ANIMAL LIFE, AND MINERALS. 



«X*{° 




§p5g?J^CM=aj^ 



The variety and luxuriance of life found on the surface of the earth are far greater than is at 
first apparent. Besides the larger species of animals and plants, myriads of microscopic forms inhabit 
the land, the water, and the air. From the burning sands of tropical deserts, to the eternal snows of 
the poles, widely differing forms occur, each being peculiarly fitted for its own conditions of growth. 

An organic form differs in many respects from one that is inorganic. The animal or plant has its 
origin in a germ ; grows from nourishment taken into its structure ; has a regular development in 
growth, passing, by successive stages, from birth to maturity, when it reproduces its kind, and passes on 
to decay and death. 

A crystal, which may be taken as the type of the inorganic world, grows by additions from without, 
does not reproduce its kind, has no regular development or growth, being perfect from its first existence, 
and has no decay or death. 



Section I, 



PLANT LIFE. 



oXKo 



CHAPTER I. 

Plant Geography. 

311. Living Matter. — All life, whether vege- 
table or animal, consists of various groupings of 

118 



cells, or approximately spherical masses, consist- 
ing of a peculiar form of jelly-like matter called 
protoplasm, composed of various complex combi- 
nations of carbon, hydrogen, oxygen, and sulphur, 
called proteids. At its beginning all life consists 
of a minute germ cell, filled with more or less 



transparent protoplasm, and containing a darker 
opaque spot called the nucleus. Examined by a 
sufficiently powerful glass, all living protoplasm 
is seen to be in constant motion, currents passing 
through the different parts in somewhat definite 
directions. 

As the germ cell develops, in all the higher 
forms of life, it multiplies, and various organs 
appear, peculiar to the form of life from which 
the germ cell was derived. All living bodies 
contain organs, and living matter is therefore 
sometimes called organic matter, to distinguish it 
from non-living or inorganic matter. 

Science has not yet disclosed the nature of the change 
whereby non-living matter is converted into living pro- 
toplasm. To produce living matter the intervention of 
already living matter is, so far as is known, absolutely 
necessary. 

312. Intermediate Position of Plants. — Proto- 
plasm forms an essential part of both plants and 
animals. Plants alone, however, possess the power 
of manufacturing protoplasm directly from inor- 
ganic or non-living matter. Plants prepare food 
for animals, who are, consequently, dependent on 
plants for their existence. Both plants and ani- 
mals are consumers of the proteid compounds. 
Plants alone are producers. In the scale of ex- 
istence plants, therefore, occupy a position inter- 
mediate between minerals and animals. 

313. Plant Geography treats of the distribu- 
tion of plant-life over the earth. 

Plant geography differs essentially from botany. Bot- 
any arranges plants into regular classes, according to pe- 
culiarities in their organs of growth and reproduction. 
Plant geography considers them only in reference either to 
the more prominent appearances, by which they give a 
distinct character to the vegetation of a country, or in 
regard to their general usefulness to man. 

In this limited view, all the minuter differences in 
structure or organization are passed over, the general form 
being the main geographical element of a plant, and the 
element with which physical geography is principally in- 
terested. 

The plants of any section of country, taken 
collectively, are called its flora. 

314. Conditions Requisite for Plant Growth. — 
Plants require for their growth certain conditions 
of light, heat, and moisture ; and since the requi- 
site amount of each of these varies with different 
species of plants, we find in every climatic zone a 
characteristic flora. The soil must contain those 
mineral ingredients which form a part of the 
structure of the plant, and, moreover, must con- 
tain them in a condition in which they can be 
readily assimilated by the plant. 



The substance of plants consists mainly of 
water derived from the air and the soil. Analy- 
sis shows that vegetable matter is composed almost 
entirely of water, and various compounds of car- 
bon, hydrogen, oxygen, and sulphur. The water 
is derived from the moisture of the soil and of the 
air ; the carbon, from the carbonic acid of the air. 
The exceedingly small proportion of mineral mat- 
ter comes directly from the soil. 

The nature of the soil, then, is far from being 
the most important element in the distribution of 
mere vegetation ; for, even when a soil is absent, 
if the other requisites of light, heat, and moist- 
ure are present, the simpler vegetable forms soon 
appear, and slowly prepare, even on a bare, 
rocky surface, a soil which is able to sustain 
higher and still higher species. This is effected 
by the breaking up of the hard mineral matter, 
and the accumulation, year after year, of the de- 
caying plants. In this way a vegetable mould is 
produced. The bare surfaces which the conti- 
nents possessed, when they first emerged from the 
oceans, gained their covering of soil principally 
in this way. 

Moisture, Heat, and Light are the prime essen- 
tials of vegetation, and it is on their distribution 
that the distribution of vegetation is principally 
dependent. 

315. Distribution of Vegetation. — The influ- 
ence of heat and moisture is noticed as we pass 
from the equator to the poles, or from the base 
of a tropical mountain to the summit. Thus 
arises a horizontal and a vertical distribution of 
vegetation. 

The greatest luxuriance of vegetation is found 
in the equatorial regions, where both heat and 
moisture are most abundant. Here a greater va- 
riety of species occurs, and the individual plants 
are larger, and more brilliantly colored, both in 
their leaves and flowers. As we pass toward the 
poles, the number of the species diminishes ; trees 
disappear, being replaced by shrubs and herbs, 
and these, in turn, by lichens and mosses, until 
finally, amid the snows of the polar latitude, 
even the simplest forms of vegetable life are 
often wanting. 

316. Horizontal Distribution of Vegetation. 

(1.) According to Meyen, we may divide the earth's 
surface into zones according to the latitude, and the moun- 
tainous elevations into zones according to the altitude. 
Since the distribution of heat is not only dependent on 
the latitude or altitude, we may advantageously modify 
this plan as has been suggested by Dove, and divide the 
zones by the isotherms. 



120 



PHYSICAL GEOGRAPHY. 



(2.) According to Schouw, we may divide the earth's 
surface into regions characterized by assemblages of pecu- 
liar floras, and separated by natural barriers. 

The great number of the regions required to give thor- 
oughness to Schouw's system, renders its use inadvisable 
in an elementary book. 

(3.) According- to Humboldt and others, we may 
divide the earth's surface into zones, according to the 
physiognomy of the plants inhabiting them. Here plants 
of entirely different species are grouped by their mere out- 
ward resemblances into what are called forms. 

The first method is the one most suitable for our pur- 
poses. We shall follow, in the main, Dove's modification, 
as adopted by A. E. Johnston, and divide the surface of 
the earth into zones, according to the isotherms, or lines 
of mean annual temperature. The values of the isotherms 
are given in round numbers. This system is based on the 
fact, that the character of the vegetation is dependent 
mainly on the temperature, which, in its turn, regulates 
the quantity of moistuTe. 

317. Horizontal Zones of Vegetation. 

(1.) The Tropical Zone, extends between the 
isotherms of 73° Fahr. on each side of the equa- 
tor. 

(2.) The Sub-Tropical Zones, extend in each 
hemisphere from the isotherm of 73° Fahr. to 68° 
Fahr. 

(3.) The Warm Temperate Zones, extend in 
each hemisphere from the isotherm of 68° Fahr. 
to 55° Fahr. 

(4.) The Cold Temperate Zones, extend in each 
hemisphere from the isotherm of 55° Fahr. to 41° 
Fahr. 

(5.) The Sub- Arctic Zone, extends in the north- 
ern hemisphere from the isotherm of 41° Fahr. 
to the September isotherm of 36.5° Fahr. 

(6.) The Polar Zone, extends in the northern 
hemisphere from the September isotherm of 36.5° 
Fahr. to the poles. 

318. The Tropical Zone, or the zone of palms, 
bananas, spices, and aromatic plants, lies on each 
side of the equator, between the isotherms of 73° 
Fahr. It includes most of the land within the 
tropics of both hemispheres. 

The excessive heat and moisture of this zone 
produce an especial luxuriance in the vegetation. 
Trees attain enormous size, the foliage is bright, 
the flowers brilliant, and the number of species 
great. The forests are characterized by the great 
variety of trees, and when allowed to attain their 
densest growth, are almost impenetrable, from the 
numerous parasitic plants with which they are 
covered, or the gigantic, rope-like climbers that 
twine among them. 

Palms, bananas, tree-like grasses, and orchids 
are among the most characteristic plants. 



Orchids are curious plants, inhabiting damp forests. 
They attach themselves to trees and rocks, drawing nearly 




Fig, 104. Palm-Trees, 

all their nourishment from the air. As a class, they are 
noted for the fragrance, vivid coloring, and curious forms 
of their flowers. The well-known vanilla bean is obtained 
from an orchid. The humble grasses of our latitude, in 
this zone, are represented by the bamboo, which often at- 
tains the height of 60 feet. 
The banyan-tree, a species of fig-tree, is found in the 




Kg, 105. Banyan-Tree, 

East Indies. From a colossal trunk numerous air-branches 
are sent out, which, descending to the ground, take root, 



Page 121. 




122 



PHYSICAL GEOGRAPHY. 



and in their turn send out other branches, and in this 
way an extended area is covered. A single tree has been 
known sufficiently large to give shade to 7000 men at the 
same time. 

The Llanos of the Orinoco are found in the 
tropical zone. During the dry season, they are 
almost entirely devoid of vegetation ; but during 
the wet season, they are covered with grasses. 

The Indian Archipelago affords an excellent illustration 
of the wonderful luxuriance of the vegetation of the 
tropics. Here the gigantic Eafflesia bears flowers three 
feet in diameter! 

In the northern and southern portions of the 
tropical zone, where the mean annual temperature 
ranges from 79° to 73° Fahr., the vegetation, 
though similar to that of the equatorial regions, 
begins to lose its density and luxuriance. The 
forests contain less undergrowth and fewer para- 
sitic plants. Tree-like ferns and figs are esjje- 
cially abundant, and some authorities have ar- 
ranged these portions into separate zones, called 
the zones of tree-ferns and figs. 

319. The Sub-Tropical Zones, or the Zones of 
Laurels and Myrtles, extend in each hemisphere, 
from the isotherm of 73° Fahr. to 68° Fahr. 
Here, the heat of summer, though sufficient to 
ripen most of the tropical fruits, is not as intense 
as in the tropical zone. The winters are mild, 
and scarcely arrest the vegetation. The palms and 
bananas of the preceding zones are still common, 
but the characteristic vegetation is found in the 
abundance of trees with thick, shining leaves, such 
as the laurels, magnolias, and myrtles. 

320. The Warm Temperate Zones, or the 
Zones of Evergreen Trees, or trees which do not 
shed their leaves, extend in each hemisphere, 
from the isotherm of 68° Fahr. to 55° Fahr. In 
this zone, trees with thick, shining leaves occur, 
mingled with oaks, beeches, and others similar to 
those found in our own forests. No palms occur, 
but in their place we find a number of glossy- 
leaved evergreen trees, and handsome evergreen 
shrubs. 

In those portions of this zone which are in the neigh- 
borhood of the Mediterranean, the bay, myrtle, laurel, fig, 
and the olive, are characteristic. The cork oaks, chest- 
nuts, and pomegranates, are frequent. The vine, said to 
be a native of this zone, attains here its greatest growth, 
the stem often reaching a thickness of half a foot. In 
America, oaks, pines, and tulip-trees occur. 

The southern warm temperate zone includes 
portions of New Zealand and Australia, and in 
South America the Pampas of the Rio de la 
Platte, where tree-like grasses abound. 



321. The Cold Temperate Zone, or the Zone of 
Deciduous Trees, or those which drop their leaves 
in autumn, extends in the northern hemisphere, 
from the isotherm of 55° Fahr. to 41° Fahr. For- 
ests of deciduous trees are the main characteristics 
of this zone ; oaks, birches, beeches, chestnuts, wal- 
nuts, maples, elms, larches, alders, and sycamores, 
are among the most common of the deciduous 
trees. Mosses and lichens frequently cover the 
trunks of the trees, and a rich and varied under- 
growth occurs ; the holly, clematis, wild rose, hon- 
eysuckle, and rhododendron, are examples. 

Extensive meadows, covered with grasses, are 
found in this zone. 

The deciduous character of the trees, and the almost 
total absence of evergreens, produce a marked contrast 
between winter and summer. During winter, the foliage 
almost entirely disappears, and snow covers the ground 
for long periods. 

This zone is essentially one of extensive forests. 
In connection with the warm temperate zone of 
the northern hemisphere, it has always contained 
the most highly civilized races of men, and is es- 
pecially rich in the number and luxuriance of its 
food-plants. 

322. The Sub-Arctic Zone, or the Zone of the 
Cone-Bearing Trees, extends in the northern hemi- 
sphere, from the isotherm of 41° Fahr. to regions 
where the mean annual temperature for the month 




Fig, 106, Pine-Trees. 

of September is 36.5° Fahr. In this zone, both 
forests and grassy meadows abound. The forests 
are especially characterized by cone-bearing trees, 
with evergreen, shining, needle-shaped leaves, such 




PLANT GEOGRAPHY. 



123 



as the pine, spruce, hemlock, cedar, and fir. In 
the northern portions of the zone, beeches and 
alders are found, and willows, when the soil is 
moist. The meadows are covered with grasses 
and flowers, and afford abundant pasturage. 

The northern limit of trees is marked on the map of 
the plant regions. 

323. The Polar Zone, or the Zone of Alpine 
Shrnbs, Mosses, Lichens, and Saxifrages, extends 
from the limits of the sub-arctic zone to the pole. 
In this zone, no trees occur except those of a stunted 
growth. Alpine shrubs, or those of tortuous, com- 
pact growth, such as the Alpine rhododendra, the 
dwarf birch, willow, and alder, occur. Sedges and 
grasses are found. The pastures of the preceding 
zones are absent ; in their place we find extended 
areas covered with lichens. 

The northern plains of Siberia are covered with exten- 
sive marshes, called Tundras, where the ground, during 
most of the year, is frozen to great depths. The short 
summers only suffice to thaw the surface, when a few 
mosses and lichens appear. 



Near the extreme northern limits of the North 
Polar zone, from the limit of the isotherm of 41° 
Fahr. for the month of July, such plants only are 
found as can thrive during the brief Arctic sum- 
mer of from four to six weeks. Shrubs are en- 
tirely absent ; lichens and mosses occur, together 
with stunted Alpine herbs. In Spitzbergen, lich- 
ens and mosses are found, the former being espe- 
cially numerous. 

324. The Vertical Distribution of Vegetation.— It 
is difficult to make a good systematic arrangement of vege- 
tation into vertical zones, since the temperature and moisture, 
on which such an arrangement must be based, are subject 
to very considerable variations. Thus, the position of the 
mountain-ranges as regards the prevalent wind, the direc- 
tion of the mountain slopes, and the extent of the elevated 
plateaus, all exert such a powerful influence on the mean 
annual temperature and the rainfall, that even in the 
same range, opposite slopes, or even different parts of the 
same slope, afford very marked climatic contrasts. In 
ranges that are widely separated, the differences are still 
greater. The following chart exhibits the characteristic 
flora in tropical America, Africa, Europe, and Asia, at 
similar elevations. 



25,000 feet. 



20,000 



15,000 



10,000 



5,000 




Fig, 107, Vertical Distribution of Vegetation. (After Black.) 



(1.) Between the level of the sea and 5000 feet, 
the vegetation is, in general, the same as in the tropical 
and sub-tropical zones. Palms, bananas, and tree-ferns oc- 
cur in the lower parts, and barley, potatoes, sugar-cane, 
rice, cotton, etc., as marked on the chart. 

(2.) Between 5000 and 10,000 feet, the vegetation 
is, in general, the same as in warm temperate zones. In 
America, the birch and cedar occur in the lower portions 
of the region, and Peruvian bark and the cinchona trees, 
so useful in medicine, in the upper portions. In Africa 
and Europe, the pine, birch, and oak occur ; and in Asia, 
the oak ; here also the vine is cultivated. 

(3.) Between 10,000 and 15,000 feet, the vegeta- 
tion, in general, is that of the cold temperate zones. De- 
ciduous trees occur ; rye, wheat, barley, and oats are cul- 
tivated. 

(4.) Between 15,000 and 20,000 feet, the flora cor- 
responds, in general, to that of the polar and arctic zones. 
A few rhododendrons and birches occur on the warmer 
Asiatic slopes, and occasionally crops of barley are culti- 



vated. The greater part of this zone is covered by eternal 
snow, as is the case with all greater elevations. 

In the descriptions here given, it will be noticed that 
the correspondence of the vertical and horizontal zones is 
but of a very general character. The names of the plants 
on the chart mark the limits at which they will grow. 

325. Plant Regions. — In some localities, a few 
plants occur over extended areas, in such vast 
numbers as to give a characteristic appearance to 
the country they cover. A brief mention will be 
made of such regions, especially as they illustrate 
the influence of the presence or absence of moist- 
ure on the vegetation. 

326. Forests occur wherever the moisture is 
abundantly and regularly distributed throughout 
the year. As a rule, forests are limited to those 
portions of the world where the rain falls at all 



124 



PHYSICAL GEOGRAPHY. 



times of the year, or is abundant during the sea- 
son the tree is growing, as in the zones of the 
variable winds. Forests may also occur in por- 
tions of the tropics where moisture is abundant. 

The forests of the cold temperate zones are de- 
ciduous; those of the other zones, evergreen. 

327. Steppes. — When the moisture is not well 
distributed throughout the year, but the rainfall 
is periodical, and long droughts occur in the in- 
tervals between the rainy seasons, the forests are 
replaced by areas called steppes, which, during 
the wet seasons, are covered with grasses, shrubs, 
or herbs ; but during the dry seasons are almost 
destitute of vegetation. Steppes are found in the 
Llanos and Pampas in South America, in the 
Great Plains of North America, in the grassy 
steppes of Australia, Russia, and Asia, in the 
German heaths, and in the African savannas. 

328. Meadows and Prairies. — These, like the 
preceding, are covered with tall grasses, but the 
vegetation is more permanent, the droughts being 
only occasional. They are found, therefore, in the 
temperate zones, in the regions of constant rains. 
An extended prairie region is found in the valley 
of the Mississippi, on both sides of the stream. 




Pig. 108. Desert Scene. 

329. Deserts are regions characterized by an 
almost entire absence of vegetation ; they are 
found mainly in the zones of the trade winds, 
and are to be ascribed entirely to the absence 
of moisture. Their bare surfaces are subject to 
great and sudden changes of temperature, being, 
as a rule, excessively warm during the day, and 
often quite cool at night. These changes are 



due to the readiness with which a bare surface 
receives and parts with heat. 



CHAPTER II. 

Cultivated Plants. 

330. Plants appear to have been originally 
confined, by conditions of soil or climate, to cer- 
tain localities. In many instances, however, plants 
furnishing materials for food, clothing, or other 
staples for the human family, have been trans- 
planted and widely diffused by man. In most of 
these cases, their successful cultivation is limited 
to regions where suitable climate and soil ex- 
isted either naturally, or have been artificially 
produced. 

331. Distribution of the Cereals. — The cereals 
include barley, rye, oats, wheat, maize or Indian 
corn, and buckwheat ; together with the potato, 
they form the more important food-plants of the 
tempei'ate zones. 

Barley, thought to be a native of Tartary and 
Sicily, can be grown farther north than any other 
grain ; in Lapland, as far as 70° N. lat. 

Rye is found as far north as lat. 67° N. in Nor- 
way. It is the most common grain in Russia, 
Germany, and in portions of France. 

Oats is probably a native of the Caucasus ; its 
northern limit in Norway is about 65° N. lat. 




Fig. 109. Maize, or Indian Corn. 



Wheat is probably a native of Tartary. It is 
the most important of the cereals, and has a wide 



CULTIVATED PLANTS. 



125 



vertical and horizontal distribution. Its northern 
limit, in Norway, is 64° N. lat. 

Maize, or Indian Corn, a native of America, is 
extensively cultivated from the southern part of 
Chili to high latitudes in North America. Its 
northern European limit is perhaps near the iso- 
therm of 65° Fahr. 

Buckwheat, probably a native of the colder 
portions of the Chinese Empire, is extensively 
cultivated in Siberia, on the plateaus of Central 
Asia, and generally in the cool temperate regions 
of the rest of the world. Buckwheat is especially 
valuable on account of the ability it possesses of 
thriving in sandy or moory soils, where other 
similar food-plants will not succeed. 

Potatoes. — The native country of the potato 
appears to have been either Chili or Peru. 
Though cultivated in both the tropical aud tem- 
perate regions, it is to be regarded as a food- 
plant of the temperate zones. It possesses a very 
remarkable range, being cultivated from the ex- 
tremity of Africa to Lapland : the requisite cold 
in the tropical regions being found on mountain- 
slopes. 

332. The Food-Plants of the Tropical Eegions, 
are riee, dates, cocoa-nuts, bananas and plantains, 
cassava, bread-fruit, sago, yams, etc. 

Rice is cultivated in tropical Africa, Egypt, 
Nubia, Persia, China, the Americas, and the West 
Indies. It requires considerable heat and an 
abundance of moisture. Rice forms the main 
food of a large portion of the world. 

Dates form an important article of food in 
North Africa, both for man and beast. Dates 
are obtained from the date-palm, a native of a 
strip of land on the southern slopes of the Atlas 
Mountains, where the tree occurs so plentifully as 
to give to the country the name of Beled-el-Jerid, 
or the Land of Dates. Different varieties of the 
date are found in the Saharan oases, and in other 
parts of the world. 

Cocoa-nuts are the product of the cocoa-palm, 
which is valuable for its food, timber, foliage, and 
fibres. The cocoa-palm is a native of Southern 
Asia, but is cultivated throughout the tropical 
regions of Ceylon, Sumatra, Java, and the islands 
of Polynesia. 

Bananas and Plantains are thought to be na- 
tives of Southern Asia. They are extensively 
cultivated throughout the tropical zones, both 
north and south of the equator. Since their 
fruit is very nutritious, and the yield of a given 
15 



area great, they form an exceedingly important 
staple of food. 




Fig. 110. Banana. 

Cassava is obtained from the manioc, a shrub 
with a fleshy root, several feet long, and nearly 
as thick as a man's arm. Tapioca is one of the 
varieties of cassava. Some species of the man- 
ioc are poisonous, when raw, but become edible 
when cooked. The manioc is a native of Brazil, 
but is abundantly cultivated in "Western Africa, 
in Congo and in Guinea. 




Fig. 111. Bread-Frnit. 

Bread-Fruit is the pulpy fruit of a tree which 
grows only in the tropics. The fruit, when baked, 
resembles potato bread in taste. The tree yields 



126 



PHYSICAL GEOGRAPHY. 



fruit during most of the year, and is said to be a 
native of the South Sea Islands, though it is now 
quite common in the Friendly and Society groups, 
and in many of the neighboring islands. 

Sago is a starchy substance, obtained from the 
pith of several species of palm trees, which grow 
in the Moluccas. A single tree is said to yield 
from 600 to 800 pounds of sago. 

Yams are the large tubers of a number of 
plants, resembling potatoes. They are cultivated 
in Africa, in South America, and in Cuba. 

333. Sugar-Cane is probably 
a native of India, but is now 
extensively cultivated through- 
out the tropical and warm tem- 
perate zones of both hemispheres, 
in the West Indies and South- 
ern United States, Guinea and 
Brazil, Mauritius and Bourbon, 
Bengal, Siam, China, Java, and 
the neighboring islands. 

334. Fruits of the Tropical 
and Warm Temperate Zones. — 
Besides those already enumer- 
ated, we find the following: 
oranges, lemons, limes, citrons, 

pine-apples, 
mangoes, figs ; 
and in the 
cooler por- 
tions cherries, 
peaches, apri- 
cots, andpome- 
granates. 

335. Distri- 
bution of 
Plants yield- 
ing Bever- 
ages. — The 
principal plants yielding beverages by infusion 
are tea, coffee, and cocoa. 

Tea consists of the dried leaves of a number 
of evergreen shrubs, natives of China or there- 
abouts. Tea is cultivated in China and India, 
from the equator as far north as lat. 45°. It ap- 
pears to thrive best between 25° and 33° N. lat. 
It is extensively cultivated in Malacca, Java, and 
in various portions of the English possessions in 
India. Tea was introduced into Europe by the 
Dutch, in 1610. 

Coffee is the berry of a tree found native in 
Abyssinia. The tree attains a height of from 




15 to 20 feet, but when cultivated, it is generally 
kept lower by cutting. The tree has shining 



Fig. 112, Sugar-Cane. 




Fig. 113, Tea-Plant. 

green leaves, and bears beautiful white flowers, 
which are followed by reddish-brown berries, each 
of which contains two grains of coffee. The 
coffee-tree is cultivated extensively in Arabia, 
Java, the Philippines, Ceylon, Brazil, and in the 
West Indies. 




Fig. 114, Coffee. 

Cocoa. — The cocoa-tree is cultivated in Central 
America, Guiana, Chili, India, Japan, and in 
several islands in the Indian Ocean. The tree 
attains a height of about 20 feet. Chocolate is 
prepared from the seed of the cocoa-tree. 

336. Spices, such as pepper, cloves, nutmegs, and 
cinnamon, are cultivated mainly within the trop- 
ics. Vanilla, used in flavoring, is also limited to 
this region. 

Pepper. — The black pepper of commerce is ob- 
tained from the dried seed of a climbing shrub, 
which grows wild on the western coasts of Hin- 



dostan. Red, or Cayenne pepper, is grown in 
Guiana and the East. 

Cloves are the dried flower-buds of an ever- 
green tree, thirty or forty feet high, which grows 
in the Moluccas. The cultivation of the tree is 
confined mainly to the little island of Amboyna. 

Nutmegs. — The tree from which nutmegs are 
obtained is found mainly on the Banda Islands, 
south of Ceram. The nutmeg is covered by 
several layers of vegetable matter, one of which 
is the mace of commerce. 

Cinnamon is the inner bark of a tree, which is 
cultivated mainly on the island of Ceylon. 

Vanilla is obtained from the dried, fragrant 
pods of a plant grown mainly in Mexico, Cen- 
tral America, and Brazil. 

337. The Principal Narcotics used in different 
countries are opium, prepared from a species of 
poppy ; the betel-plant, a native of Hindostan : 
the leaves of the betel-plant are chewed, together 
with the areca-nut ; hasheesh, a narcotic used in 
India ; and tobacco, the dried leaves of a plant 
grown extensively in Mexico, Cuba, Brazil, and 
in the United States. 

338. Plants Valuable as giving Materials for 
Clothing, are cotton, hemp, and flax. 

Cotton, a native of India, is now grown exten- 



sively in East India, Persia, on the eastern shores 
of the Mediterranean, in various parts of Europe, 
and in North and South America. 

Hemp and Flax are cultivated in the temper- 
ate regions of Kussia, and throughout Great 
Britain and the United States. 

The plants producing medicines, and products 
employed in the arts or manufactures, are : 

The Cinchona-Tree, found on the upper slopes 
of the tropical Andes. Quinine is obtained from 
the bark of the tree. 

Gum Arabic, obtained from the East Indies, 
Egypt, and Africa. 

Indigo, a blue dye, obtained from the indigo- 
bearing plants. 

Brazil-Wood, Nicaragua-Wood, and Log-Wood, 
yield reddish dyes. 

Quercitron and Black Oak, yield a yellow dye. 

Turpentine and Bosin, are products of the pine 
tree. 

Caoutchouc, or India-rubber, is the juice of 
several tropical plants. 

Olive Oil is derived from the olive-tree, culti- 
vated on the borders of the Mediterranean. 

Cocoa-nut, Palm, Flaxseed and Cotton-Seed 
Oils, are obtained respectively from the cocoa- 
nut, palm-tree, and the seeds of flax and cotton. 



SYLLABUS. 



All life consists of groupings of cells or spherical masses, 
consisting of a transparent jelly-like substance called pro- 
toplasm. 

All life originates in a germ cell produced through the 
agency of pre-existing life. 

Protoplasm forms an essential part of all plants and ani- 
mals. Both plants and animals consume protoplasm dur- 
ing their growth. Plants, alone, produce protoplasm. Ani- 
mals are dependent on plants for their existence. 

Plants require for their vigorous growth certain condi- 
tions of light, heat, moisture, and soil ; of these, heat and 
moisture are the most important. 

Plant geography treats of the distribution of plants. It 
differs essentially from botany, which treats of the pecu- 
liarities in the structure of plants. 

The plants of any section of country, taken collectively, 
are called its flora. 

The differences in the distribution of heat and moisture, 
produce corresponding differences in the distribution of 
vegetation. The distribution of heat and moisture, there- 
fore, forms the true basis for the distribution of plant life. 

If a soil be wanting in any section of country, but the 
proper conditions of light, heat, and moisture be present, 



the simpler vegetable forms will appear, and gradually 
prepare a soil fitted for the higher kinds of vegetation. 

The variety and luxuriance of vegetation decrease as 
we pass from the base to the summit of a mountain, or 
from the equator to the poles; this decrease is caused 
by a corresponding decrease in the amount of heat and 
moisture. 

According to the horizontal distribution of plants, the 
surface of the earth is divided into the following zones : 
the tropical, sub-tropical, warm temperate, cold temper- 
ate, sub-arctic, and polar. 

The tropical zone is characterized by the prevalence of 
palms, bananas, spices, and aromatic plants. 

The sub-tropical zones are characterized by the preva- 
lence of laurels, myrtles, and magnolias. 

The tropical and sub-tropical zones, especially the 
former, are particularly characterized by an especial 
luxuriance of their vegetation. 

The warm temperate zones are characterized by forests 
of evergreen trees. 

The cold temperate zones are characterized by forests 
of deciduous trees. 

Deciduous trees are those which cast their leaves in 



128 



PHYSICAL GEOGRAPHY. 



autumn. Oaks, birches, beeches, chestnuts, walnuts, ma- 
ples, elms, larches, alders, and sycamores are among the 
most common of the deciduous trees. 

Extensive grass-covered meadows are found in the cold 
temperate plant zones. 

The sub-arctic zone is characterized by cone-bearing 
trees. The polar zone, by Alpine shrubs and mosses. 

Forests require, for their luxuriant growth, an abun- 
dance of moisture, evenly distributed throughout the 
year, or during the time the trees are growing. 

Steppes are regions covered with a scanty vegetation; 
they are produced either by insufficient moisture, or its 
irregular distribution throughout the year. 



The principal cereals are barley, rye, oats, wheat, maize, 
corn, and buckwheat. 

The principal food-plants of the tropical regions are 
rice, dates, cocoa-nuts, bananas, plantains, cassava, sago, 
yams, and bread-fruit. 

Some of the most important plants cultivated for the 
beverages they yield, are tea, coffee, and cocoa. 

The principal spices are pepper, cloves, nutmegs, and 
cinnamon. The principal narcotics are opium, betel, 
hasheesh, and tobacco. 

Cotton, hemp, and flax are valuable as furnishing mate- 
rials for clothing. 

The cinchona-tree yields quinine. 



REVIEW QUESTIONS. 



-oo^O 



What is protoplasm ? Of what does all life consist? 

In what respect are animals dependent upon plants for 
their existence ? 

Define plant geography. In what respect does it differ 
from botany? Name the conditions requisite for plant 
growth. 

How do these conditions compare with each other in 
importance ? Describe the formation of soil. 

Why is soil of comparatively less importance to the ex- 
istence of vegetation than heat or moisture? 

What do you understand by the horizontal distribution 
of vegetation ? By the vertical distribution ? 

What is the main cause of the difference in the flora of 
different parts of the world ? 

Why should the isothermal lines generally form the 
boundaries of the plant zones? 

Name the horizontal zones of vegetation. 

State the boundaries of each of these zones. 

What is the characteristic flora of the tropical zone ? 

Why should the vegetation of the tropics be so much 
more luxuriant than that of the rest of the world? 

Why should the same change be noticed in the vegeta- 
tion of a high tropical mountain, in passing from its base 
to its summit, as in passing along the earth's surface from 
the equator to the poles ? 

Describe the vertical vegetable zones. To what hori- 
zontal zone does each of these correspond? 

Name the conditions requisite for the luxuriant growth 



of forests. How do the forests of the cold temperate zones 
differ from those of other zones? 

By what climatic conditions are steppes produced? 

What conditions are requisite for the production of 
meadows and prairies ? How- are deserts produced ? 

Name some of the more important cereals. 

Which of the cereals form the principal food-plants of 
the temperate zones? Which of the cereals has the far- 
thest northern range? Which is the most important? 

Name the principal food-plants of the tropical regions. 

What is the principal region for the cultivation of 
dates? Name the principal regions in the world noted 
for the successful cultivation of the sugar-cane. 

Name the fruits of the tropical and warm temperate zones. 

In what portions of the world is coffee successfully cul- 
tivated ? Where is tea cultivated ? 

From what tree is chocolate obtained? 

From what plant is black pepper obtained? Where is 
the plant cultivated? 

From what are cloves obtained ? Where is the tree cul- 
tivated? Where are nutmegs grown ? What is mace? 

In what part of the world is cinnamon cultivated? 

Name the principal narcotics used in different parts of 
the world. 

Name the plants which furnish valuable materials for 
clothing. 

From what tree is quinine obtained ? 

Name some of the principal vegetable dyes. 



MAP QUESTIONS. 



«XKo 



Trace on the map showing the distribution of vegeta- 
tion, the parts of the world included in the tropical 
zone. 

Name the plants of the tropical zone which are charac- 
teristic of South America. Name those of Africa. Of 
India and Australia. 

Describe the principal region of the cocoa-nut palm, 
bread-fruit, sago, and yam in the eastern continent. 

Describe from the map the limits of the sub-tropical 
zones. Describe the characteristic flora of those por- 
tions of each of the continents which lie within these 
zones. 

Describe the limits of the warm temperate zones. Of 



the cold temperate zones. Of the sub-arctic zone. Of the 
polar zone. 

Trace on the map the northern limit of trees. Trace 
the southern limit of trees. 

Name some of the trees of the warm temperate zones. 
Of the cold temperate zones. Of the sub-arctic zones. 

In what parts of the world are pasture-lands found? 

Name the characteristic plants of the regions which lie 
north of the arctic circle. 

Trace on the map showing the vertical distribution of 
vegetation, the characteristic plants found in Africa, be- 
tween the level of the sea and 5000 feet. In Europe. In 
Asia. In America. 



ZOOLOGICAL GEOGRAPHY. 



129 



Section II. 



ANIMAL LIFE. 



oX*5° 



CHAPTER I. 

Zoological Geography. 

339. Zoological Geography treats of the dis- 
tribution of animal life. The animals found in 
any region of country are called its fauna. Like 
plants, animals appear to have been originally 
created in certain localities, from which they have 
spread, more or less, over adjoining areas. 

Though able to move about freely from place 
to place, animals are, nevertheless, restricted, by 
conditions of food and climate, to well-defined 
areas. Animals derive their sustenance, either 
directly or indirectly, from plants. 

340. Distribution of Animal Life. — The distri- 
bution of heat, moisture, and vegetation forms the 
true basis for the distribution of animal life. 

We distinguish a horizontal and a vertical dis- 
tribution of animal life. 



As a rule, the luxuriance and diversity of ter- 
restrial animal life decrease as we pass from the 
equator to the poles. A similar decrease is no- 
ticed in passing from the coasts of the continents 
toward the interior. Within the tropics, where 
the abundant heat and moisture produce a vigor- 
ous vegetation, all forms of terrestrial animal life, 
save man, attain the greatest development in size, 
intelligence, and activity. As we proceed toward 
the poles, the species are less developed, although, 
in the temperate regions, large and vigorous ani- 
mals are still numerous. In the polar zones, the 
reindeer and white bear are the only representa- 
tives of the larger land animals. 

In marine animal life, the law of distribution 
is reversed, both the number and size of the 
species increasing from the equator toward the 
poles. This is probably due to the more equable 
temperature of the ocean in high latitudes. 

341. The Vertical Distribution of Life.— In 



25,000 feet. 



20,000 



15,000 



5,000 




Fig, 115. Vertical Distribution of Animal Life. (After Black.) 



passing from the base to the summit of a tropical 
mountain, the same change is noticed in the spe- 
cies of animals, as in passing along the surface of 
the earth from the equator to the poles. 

In the above chart, the names of the animals 
are placed at the greatest elevation at which they 
are found. The power of locomotion possessed by 
animals renders it extremely difficult to arrange 
the fauna in zones according to the altitude. In 



general, however, the animals found on the slopes 
of tropical mountains, at elevations included be- 
tween the sea-level and from 5000 to 7000 feet, 
correspond to those inhabiting the tropical zone ; 
between 5000 or 7000 feet and 15,000 feet, to 
those of the temperate zones. The condor is 
found in the high Andes, far above the snow 
line. 
The fauna of high mountain-ranges are often sharply 



130 



PHYSICAL GEOGRAPHY. 



marked. A particular species, at a given elevation on one 
range, is frequently entirely wanting on a neighboring 
disconnected range, even when the same conditions of 
heat, moisture, and vegetation exist. The temperature 
of the intervening lower country, through which the ani- 
mals would have to pass in order to reach the adjoining 
6lopes, forms an impenetrable barrier. 

342. Natural Boundaries of Zones of Animal 
Life. — Large bodies of water, deserts, or moun- 
tain-ranges, mark the boundaries of regions of 
animals as well as of plants ; but the influence 
of temperature is so important, that even when 
these natural barriers are wanting, the horizontal 
range of animals is sharply marked by the iso- 
thermal lines. 

In North America, there are well-marked zones of ani- 
mals, which extend from east to west across the continent. 
Here, although no natural barriers exist to limit the wider 
range of the animals, yet they seem unable to permanently 
pass the limits of the isotherms, which mark the climatic 
conditions necessary to their vigorous growth. This in- 
ability doubtless arises from the distribution of the flora, 
on which, directly or indirectly, they are dependent for 
their food. 

343. Acclimation. — The power of becoming 
acclimated, or being able to live in a climate dif- 
fering from that in which they were first created, 
appears to be possessed by animals, as a class, to 
an exceedingly limited extent. 

Man, and his faithful friend, the dog, form an exception 
to most other animals in this respect. They are able to 
endure both the severe heat of the tropics, and the rigor 
of the Arctic regions. The reindeer thrives amid the 
snows of Lapland or Greenland, but perishes from the 
heat of St. Petersburg. Monkeys are indigenous to the 
tropics, but die with consumption, even in the compara- 
tively mild climate of the north temperate zones. 

344. Horizontal Distribution of Animal Life. 

— The vast number of species of animals, the pe- 
culiar laws of their growth, and their power of 
adaptation to change of circumstances, render 
their accurate distribution into zones or regions 
a task far beyond the scope of an elementary 
book. It will be sufficient for our purpose to 
divide the fauna of the earth into those found, in 
general, in the three mathematical climatic zones : 
the Torrid, the Temperate, and the Polar. The 
accurate limits of these zones would be found in 
the isotherms, but in a general description, little 
difference would be noticed. On the map, the 
actual limits of some of the more important ani- 
mals are given. These limits, it will be noticed, 
in most cases follow the general direction of the 
isotherms. 

345. Characteristic Fauna. — A careful study 



of the map of the distribution of animal life, will 
show that each continent possesses a fauna pecu- 
liar to itself. This arises, generally, from some 
clearly traceable peculiarity in the distribution 
of the heat and moisture, or in the nature of the 
vegetation. Some of these peculiarities will be 
discussed in a brief review of the characteristic 
fauna of each of the continents. The following 
are the characteristic tropical, temperate, and arc- 
tic fauna. 

346. Tropical Fauna. — The abundance of 
heat, moisture, and vegetation of the torrid 
zone causes its fauna to excel all the others 
in the number and diversity of terrestrial 
species, as well as in their size, strength, and 
sagacity. 

The following animals are found mainly within 
the regions of the earth included between the 
Tropics of Cancer and Capricorn. 

Mammalia are represented as follows : 

Monkeys, by the man-like orang-outang, the 
chimpanzee, gorilla, baboon, and other species. 




Pig. 116, Lion, 

Carnivora, or flesh-eating mammals, by the lion, 
tiger, panther, and puma. 

Herbivora, or plant-eating mammals, by the ele- 
phant, rhinoceros, tapir, and hippopotamus, the 
horse-like zebra and quagga, the giraffe or camel- 
opard, and the camel. 

Cetaeea, or ivhales, by the sperm whale, found 
only in tropical or temperate waters. 

Cheiroptera, or bats, by a number of species. 

Marsupials, by the kangaroo of Australia. 

Birds are represented, in tropical regions, by 



Page 131. 




132 



PHYSICAL GEOGRAPHY. 



species noted for their great size and strength, or 
for the brilliant colors of their plumage. Among 
those noted for their size may be mentioned the 
condor, ostrich, eagle, ibis, flamingo, and cassowary; 
among those especially noted for their plumage, 
the birds of paradise, peacock, and parrots, and 
the humming-birds of South America, which lat- 
ter, though in less brilliantly-colored plumage, 
extend nearly to the extreme limits of the north 
and south temperate zones. 




Fig. 117. Alligator. 

Reptiles are represented by the crocodile, alli- 
gator, iguana, gigantic lizards, and turtles ; among 
serpents, the enormous boa-constrictor, and num- 
bers of hooded and other venomous serpents. 

The Fish of tropical waters, though large and 
brightly colored, are not so well adapted for food 
as the more sombre varieties of the temperate or 
colder waters. 

347. Temperate Fauna. — The following ani- 
mals are found mainly between the tropics and 
polar circles. Though fewer of the higher spe- 
cies of animals are found in the temperate zone 
than in the torrid zone, yet many of the fauna 
are of large size, and among them are found ani- 
mals most useful to man. 

The physical tropical zone, as will be seen from an in- 
spection of the map of plant life, actually extends, in the 
eastern continent, far into the mathematical north tem- 
perate zone, and in these portions the corresponding trop- 
ical species occur. Thus, in Northern Africa and South- 
ern Asia, are found the ape, tiger, lion, panther, camel, and 
rhinoceros. 

Mammalia are represented as follows : 
Flesh-eating mammals, by the lynx, hyena, wolf, 
jackal, dog, fox, raccoon, bear, seal, and walrus. 
Plant-eating mammals, by the wild boar and hog, 



the horse, ass, ox, sheep, goat, and chamois, many 
of which have been domesticated, as the moose, 
elk, reindeer, stag, antelope, buffalo, camel, llama, 
and numerous others. 

Cetacea, or whales, by the sperm and white 
whales. 

Rodentia, or gnawing mammals, by the beavers, 
squirrels, rats, and porcupines. 

Marsupials, by the kangaroo of Australia. 

The birds of the temperate zones are repre- 
sented by the condor, vulture, hawk, eagle, owl, 




Fig, 118. Eagles, 

and parrot (near the southern limit of the zone). 
The turkey, pheasant, and our common domesti- 
cated fowls also are natives of this zone. Here 
occur numerous birds which are noted for the 
sweetness of their song, as the wren, thrush, robin, 
nightingale, and lark; the pelican, albatross, and 
the cassowary are found in this zone. 

Reptiles are represented by the alligator, croco- 
dile, and lizard, and the rattlesnake, copperhead, 
and various other serpents, both poisonous and 
harmless. 

348. Arctic Fauna. — The following animals 
are found mainly between the polar circles and 
the poles. The south arctic fauna is but little 
known ; the following description, therefore, re- 
fers mainly to the northern hemisphere: 

In the arctic regions of the world, the large 
land animals are, with a few exceptions, replaced 
by numerous smaller furry species. Throughout 



CHARACTERISTIC FAUNA OF THE CONTINENTS. 



133 



the northern portions of the north temperate 
zone, and the southern portions of the arctic, 
fur-bearing animals are especially numerous and 
valuable. 

The white polar bear, the reindeer, moose, and 
the mush-ox, are among the largest of the land 
species ; but in warmer regions of the oceans, nu- 
merous species exist, of which the whale is among 
the largest of the animal world. 

The Greenland whale, which sometimes attains the length 
of seventy feet, and is covered with blubber to a thick- 
ness of two or three feet, is found only in this zone. A 
similar, though smaller, species occurs in the southern 
waters. The seal and walrus are also found in this zone. 




Fig, 119. Seals aad Walrus. 

Besides the larger animals, numerous smaller 
species, such as minute zoophytes, mollusks, and 
crustaceans, which form the food of the whale, 
and which, in some places, exist in immense 
numbers, inhabit the waters. Among birds, in- 
numerable water-fowl occur. 

«>xk<^ 

CHAPTER II. ■ 

Characteristic Fauna of the Conti- 
nents. 

349. Characteristic Fauna of the Continents. 

— Each of the continents is characterized by some 
peculiarity in its fauna. This peculiarity arises 
either from the nature of the vegetation, or the 
distribution of the heat and moisture, and affords 



an excellent example of the intimate connection 
between the physical features of a country, and 
its flora and fauna. Only the general character- 
istics of the fauna will be given. 

For the particular animals inhabiting each continent, 
the student is referred to the map of the distribution of 
animal life. 

350. North American Fauna. — The chief cha- 
racteristic of the North American fauna is found 
in the preponderance of plant-eating mammals. 
This feature is due to the abundance of pasture- 
lands, and their luxuriant vegetation. From its 
extensive lake and river systems, North America 
is peculiarly fitted to sustain aquatic life ; hence, 
its numerous water-fowl and beaver. 

351. Fur-bearing animals are particularly nu- 
merous and valuable. Three natural districts of 
fur-bearing animals exist : the forest region, the 
prairie region, and the barren regions of the 
north, each of which is characterized by a pecu- 
liar fauna. 

Forest Region — Here, among carnivora, are found the 
Mack bear, marten, ermine, mink, otter, the silver fox, the black 
fox, and the lynx; among the rodentia, the beaver and 
musk-rat; and among the ruminants, the moose and rein- 
deer. The wolverine and wolf are found both in the for- 
est region and the barren grounds. 

Barren Grounds. — The brown and polar bears, the polar 
fox, and the polar hare are characteristic. 

Prairie Region. — The grizzly bear, the most formidable 
animal of the continent ; the prairie wolf, and the gray fox 
are also found here. 

The puma, or the American lion, which is found 
also over the greater part of South America, is 
the most powerful representative of the lion and 
tiger tribe of the East. 

352. South American Fauna. — The chief cha- 
racteristics of the South American fauna arise 
from the extreme luxuriance of its vegetation, 
due to the abundance of its moisture. In vast 
districts, as the Selvas of the Amazon, the vege- 
table world usurps the ground nearly to the ex- 
clusion of the higher forms of animal life. The 
fauna is, therefore, as a rule, characterized by its 
fitness for existing in connection with either an 
abundance of water or of vegetation. 

Insect Life is peculiarly characteristic of the 
continent. Nowhere else are the species so nu- 
merous, so brilliantly colored, or so large. Here 
are found the largest of the beetles, and the most 
beautiful of the butterflies. 

Reptiles are largely represented. They find, 
in the tepid, sluggish waters of the huge rivers, 
conditions most favorable to rapid growth. Here 



134 



PHYSICAL GEOGRAPHY. 



live the crocodile, gigantic lizards, and many 
venomous serpents. 

Among Birds, the water species are in the as- 
cendance. Humming-birds, which occur also in 
North America, are found in great abundance in 
the southern continent. The condor is found on 
the higher slopes throughout the Andes ; the os- 
trich, toucan, and parrot are also characteristic. 

Among the Mammalia, the ant-eaters and sloths 
peculiarly characterize the continent. The tapir 
and peccary are the only representatives of the 
elephant, rhinoceros, and hippopotamus of the 
Eastern continents. The llama, puma, and the 
prehensile-tailed monkeys are also characteristic 
of the region. 

The South American district of fur-bearing animals ex- 
tends through parts of Chili and the Argentine Eepublic. 
The marsh beaver is the principal animal. 

353. Asiatic Fauna. — From the great mass of 
land within the tropics, the fauna of Asia, besides 
its numerous arctic and temperate species, contains 
a great variety of tropical forms. 

Taken in connection with Northern Africa, 
Asia is essentially the region of extensive dry 
plains and arid tracts. The vegetation through- 




Pig. 120, Elephant. 

out its temperate climes is greatly inferior to that 
of America, but its animal life is marked by a 
much greater variety in the higher forms. Fore- 



most among these are the man-like monkeys, the 
orang-outang, the elephant, the royal tiger, and 
others. Fur-bearing animals are also numerous. 
Among birds, those with bright, gay-colored 
plumage abound. Reptiles also are repre- 
sented, though not to such an extent as in 
South America. 

When we bear in mind that in Asia, the horse, 
ass, goat, sheep, camel, swine, elephant, buffalo, 
and ox are found in great numbers, it will be 
seen that Asia, the home of primitive man, is 
also peculiarly the home of domesticated animals ; 
that is, of the animals which man has trained to 
labor for him. 

The Asiatic district of fur-bearing animals includes Si- 
beria, Kamtchatka, and the basin of the Amoor Eiver in 
Mantchooria. The following animals are characteristic: 
the brown bear, badger, weasel, ermine, sable, otter, marten, 
and many others. The furs of the sable, black fox, otter, 
and the ermine, are considered the most valuable. 

354. African Fauna. — The peculiarities of the 
northern portion of the continent have been al- 
ready pointed out in connection with Asia. It is 
a fact worthy of notice, that the great deserts of 
the world, like the Sahara, though nearly desti- 
tute of any vegetation, are able to sustain many 
of the highest species of animals. 

Over these tracts are found the lordly lion, the 
leopard, and the panther, and the numerous ani- 
mals on which they prey, such as the antelope, 
the zebra, the quagga, and others. All these 
possess powers of rapid locomotion, which pe- 
culiarly fit them for the arid plains over which 
they roam. 

In the remaining portions of Africa, the luxu- 
riant vegetation is capable of sustaining animals 
of a larger growth. Here occur the largest of 
the Mammalia, such as the elephant, rhinoceros, 
and hippopotamus ; here also is found the giraffe, 
the largest of the ruminantia ; man-like monkeys 
are also characteristic. 

355. Australian Fauna. — The more nearly per- 
fect isolation of Australia than any of the other 
continents, together with the peculiar distribu- 
tion of its heat and moisture, causes its fauna 
and flora to differ markedly from those of all 
the other continents. 

Australia is essentially the home of the marsu- 
pials. These are both carnivorous and herbivor- 
ous. The kangaroo is, perhaps, the most cha- 
racteristic of the marsupials. Large and power- 
ful animals are entirely absent ; in this respect 
the continent offers a sharp contrast to Africa. 



DISTRIBUTION OF THE HUMAN RACE. 



135 



The birds are also of peculiar species, such as the 
emu, cassoicary, dodo, and apterix. 



CHAPTER III. 

The Distribution of the Human 
Race. 

356. Ethnography is that department of phys- 
ical geograjshy which treats of the varieties of 
the human race, and their distribution. 

The range of the distribution of man is much 
greater than that of the lower animals, which, as 
we have already seen, with the trifling exception 
of a few that have been domesticated, are confined 
to certain limited localities. Man has far greater 
powers of adapting himself to a change of cir- 
cumstances, and is found in nearly all the climatic 
zones, from the equator to the poles, and at all 
elevations, from the level of the sea to the edge 
of the snow line. 

357. Unity of the Human Race. — Although 
the different races of men vary greatly in color, 
size, stature, and intelligence, still a number of 
circumstances point to their descent from a single 
family or species. 

(1.) The Anatomical Structure is invariably 
the same in all races. 

(2.) Gradual Modification of Types presented 
by the different races. The more marked out- 
ward peculiarities, which serve as the basis for 
classification, pass into each other, by almost in- 
sensible gradations, from the highest race to the 
lowest. This points to a gradual modification of 
a single, original race by changes in external cir- 
cumstances, thus producing the present varieties. 
It would appear that all the varieties of the race 
have descended from the Caucasians, or whites. 

(3.) Similarity of Earlier Myths and Legends. 
Since the earlier myths and legends of nearly all 
nations resemble each other, it is fair to infer that 
their remote ancestors originally dwelt together. 

(4.) Close Eesemblance of Language of Widely 
Separated Eaces. This may be regarded as the 
strongest proof of unity. 

If we examine the words used in different na- 
tions to express the most common ideas, we will 
find a remarkable similarity between many of 
them. For example, our word father is pita in 
Sanscrit, pater in Latin, pater in Greek, voter in 
German, and pere in French. The same similar- 



ity is noticeable in the words for mother, sister, 
brother, daughter, God, and many others. The 
only rational explanation for the resemblance is, 
that the words were derived from the same parent 
language, the present differences having been 
gradually acquired, as the descendants of this 
earlier people wandered farther and farther from 
their common home. 

An extended comparison made in this way between dif- 
ferent languages, has shown the common origin of the lan- 
guages of Europe and a large part of Asia. It has been 
conclusively proved that these tongues owe their origin 
to one parent nation, which dwelt, during pre-historic times, 
in the neighborhood of Mt. Ararat and Mesopotamia. 

Other families of languages, such as the Chinese and 
Semitic, have been studied, but thus far the connection 
between the different families has not beeu certainly es- 
tablished. 




NEGRO. MONGOLIAN. 

Fig, 121. Primary Races of Men, 

358. The Eaces of Men. — Among the varieties 
of the human race, three strongly-marked types 
are found : the Caucasian, the Mongolian, and 
the Negro. These, which may be regarded as the 
primary races, are grouped around three geograph- 
ical centres, which correspond nearly to the cen- 
tres of the three divisions of the Old World. 

The Caucasian type is found in most of Europe 
and in South-western Asia ; the Mongolian type, 
in those parts of Europe and Asia not occupied 
by the Caucasian ; the Negro type, in Africa. 
The other parts of the world are peopled mainly 
by three other races, which, in general, bear close 
resemblances to the preceding. These are the 
Malay, the American, and the Australian. They 



Page 136. 




DISTRIBUTION OF THE HUMAN RACE. 



137 



are called the secondary races, and appear to be 
modifications of the Mongolian. 

359. Cranial Characteristics. — The primary races are 
sharply distinguished by the following types of skull : 

Caucasian. The skull is nearly oval, and the arch of 
the cheek-bones moderate. 

Mongolian. The skull is nearly round, the occipito- 
frontal diameter, or the distance from the forehead to the 
back of the head, is slightly greater than the parietal 
diameter, or that between the temples. 

Negro. The skull is elongated from the back of the 
head to the forehead ; that is, the occipito-frontal diam- 
eter greatly exceeds the parietal. The cheek-bones are 
large and projecting. 

360. The Caucasian, or White Race is charac- 
terized by a round or oval head ; symmetrical 
features ; vertical teeth ; round or oval face ; 
arched forehead; fair complexion, and ample 
beard. 

The Caucasian race inhabits South-western 
Asia (Hindostan, Persia, and Arabia), Northern 
Africa, and nearly the whole of Europe. The 
descendants of the race now people large portions 
of America, Australia, and Southern Africa. 

361. Divisions of the Caucasian Race. — The 
Caucasian race may be divided into three branches : 
the Hamilic, the Semitic, and the Japhetic. 

(1.) The Hamitic Races originally inhabited 
Palestine, the shores of the Arabian Peninsula, 
and the valley of the Nile. They are now, how- 
ever, scarcely distinguishable from the other 
branches of the Caucasian race, with whom they 
have intermarried. 

(2.) The Semitic, or Syro-Arabian Races, com- 
prise the modern Syrians, the Jews or Hebrews, 
the inhabitants of Arabia and Abyssinia, and the 
greater part of Northern Africa. 

Among the ancient peoples belonging to this branch of 
the Caucasian race, are the Assyrians and Babylonians, 
the Israelites, Moabites, Ammonites, Edomites, Ishmael- 
ites, and Phoenicians. 

(3.) The Indo-Earopeans, or the Aryan Race, 
comprise the Japhetic race. They are the most 
civilized peoples of the world, and include the 
following nations: 

(1.) Celtic Nations, including the Irish, Welsh, Scots, and 
the Bretons of France. 

(2.) Romanic Nations, comprising the Italians, Spaniards, 
Portuguese, and the French. 

(3.) The ancient Greeks. 

(4.) Germanic Nations, comprising the Germans, Anglo- 
Saxons (English), Dutch, Flemish, Danes, Swedes, and the 
Norwegians. 

(5.) Slavonic Nations, comprising the Eussians, Poles, 
Croats, and Czechs. 

(6.) Nations of the Iranian Plateau, comprising the Per- 
sians, Belooches, and the Afghans. 

(7.) The Hindoos. 
16 



362. The Mongolian, or Yellow Race.— The 
chief characteristics of the Mongolian race are : 
broad head ; angular face ; high cheek-bones ; 
small, obliquely-set eyes ; straight, coarse, black 
hair ; scanty beard, and short stature. The color 
of the skin varies from pale lemon to brownish 
yellow. 

The Mongolian race includes the inhabitants 
of all of Asia, except a small part of the Malay 
Peninsula, and those portions of the continent 
occupied by the Caucasians. It also includes the 
Lapps and Finns, inhabiting the northern por- 
tions of Europe, the Turks of Europe, and the 
Magyars of Hungary, In America, the race is 
represented by the Esquimaux, who inhabit 
Greenland and the northern borders of the 
North American continent. 

In Central Asia, the race is represented by the Thibetans, 
Chinese, Indo-Chinese, and others. 

In Northern Asia, by the Samoides, inhabiting the shores 
of the Arctic Ocean, from the Petchora to the Yenisei, and 
south to the Altai Mountains ; the Ugrian, or Finnic races, 
inhabiting the upper valley of the Obe, and a part of 
Northern Europe ; the Tchooktchees, the Tungusians, and 
the Yakuts, of North-eastern Asia. 

Other branches of the race, are the Coreans, Japanese, 
Kamtchatdales, Koriaks, and the Mongols. 

363. The Negro, or Black Race.— The chief 
characteristics of this race are : narrow and elon- 
gated head ; crisp and curly hair ; projecting 
jaws; thick lips; soft and silky skin; color black 
or dusky ; scanty beard, especially on upper lip ; 
broad feet, and projecting heel-bones. 

The race inhabits the entire continent of 
Africa, excepting those parts occupied by the 
Caucasians. 

The following are the most important varieties of the 
race : the Jaloffs, Mandingoes, and Ashantis, in the west- 
ern part ; the Tibboos, in the north central ; the Gallas, 
in the eastern ; the Congo Negroes, in the south central ; 
and the Hottentots and Kaffirs, in the extreme south. 

The Negro tribes differ greatly in their civili- 
zation : the Gallas, though cruel and vindictive, 
are a handsome, gifted race ; the Hottentots, on 
the contrary, are among the most debased creat- 
ures in existence. 

364. The Secondary Races. — The Malay, or 
Brown Race ; the Australian ; and the American, 
or Copper-colored Race, are modifications of the 
Mongolian Race. 

365. The Malay, or Brown Race.— The princi- 
pal characteristics of this race are the same as 
those which distinguish the Mongolian ; the eyes, 
however, are horizontal, the face flat, and the hair 



138 



PHYSICAL GEOGRAPHY. 



less coarse and straight. The color of the skin 
varies from a clear brown to a dark olive. In 
the Papuans, it is dark brown, and even black. 




AUSTRALIAN. 



AMERICAN INDIAN. 



Fig. 122. Secondary Kaces of Men. 

This race inhabits the southern part of the 
Malay Peninsula, the island of Madagascar, and 
the islands of the Indian and Pacific Oceans. 

The different peoples included under the Malay 
race present the most strongly marked contrasts. 
The Papuans, for example, differ widely in their 
appearance from the normal Malay. They are, 



perhaps, allied more closely to the Australians 
than to any others. 

366. The Australian Race is to be regarded as 
a sub-variety of the Papuan branch of the Ma- 
lays. It inhabits all the continent of Australia 
not settled by the whites. 

The Australian race possesses the following 
characteristics : the head is large ; eyes deep-set ; 
nose broad; hair dark; beard abundant. The 
color of the skin varies from dark brown to deep 
black. The Australians are almost wholly desti- 
tute of civilization. 

367. The American, or Copper-colored Race, 
though containing many widely differing varie- 
ties, yet possesses, in some respects, many com- 
mon features. Its general resemblance to the 
Mongolian is evident, but the top of the skull is 
more rounded, and the sides less angular. This 
race, though once numerous and powerful, is now 
rapidly disappearing before the whites. 

In Lower California, Mexico, Peru, and Bra- 
zil, the old races have become mixed with Span- 
ish and other elements. 

The ruins of temples, and once populous cities, are com- 
mon on the high Andean plateaus. These parts of the 
earth were inhabited at the time of the discovery of tho 
continent by a people who had made considerable progress 
in the art of working metals, and who were probably of 
Asiatic origin. 

The plateaus of Central America contain the traces of a 
still higher, though more ancient civilization, the origin 
of which is unknown, though some trace it to a Semitic 
or an Egyptian source. 



SYLLABUS. 



-»oj*<o 



The animals of any section of country are called its 
fauna. 

Notwithstanding their powers of locomotion, animals 
are restricted, by conditions of food and climate, to well- 
defined areas. 

Since animals are dependent for their existence upon 
plants, the heat and moisture of any given section of 
country form the true basis for the distribution of its 
fauna. 

We distinguish a horizontal and vertical distribution 
of animal life. 

The same change is noticed, in the species of animals, 
in passing from the. base to the summit of high tropical 
mountains, as in passing along the surface of the earth 
from the equator to the poles. 

Terrestrial animal life attains its greatest development, 
both as regards luxuriance and diversity, within the 
tropics. 



Marine animal life attains its greatest development in 
the colder waters of the polar regions and vicinity. 

Man attains his greatest mental development in the 
temperate zone. 

As regards the vertical distribution of life, the. fauna of 
regions between the sea level and 5000 or 7000 feet, resem- 
bles, in general, that of the tropics ; between the preced- 
ing and 15,000 feet, that of the temperate zones. 

The boundaries of animal regions are, in general, to be 
found in the isothermal lines. 

As a class, animals appear to possess to but a limited de- 
gree the power of living in a climate differing greatly 
from that in which they were first created. 

The fauna of the earth may be conveniently arranged 
under three heads : the tropical, temperate, and arctic. 

The tropical fauna are characterized by the number and 
diversity of terrestrial species, as well as their size 
strength, and sagacity. 



KEVIEW QUESTIONS. 



139 



In tropical fauna, the mammalia are represented as fol- 
lows: 

Monkeys, by the orang-outang, chimpanzee, gorilla, and 
baboon. 

Flesh-eating mammals, by the lion, tiger, panther, and 
puma. 

Plant-eating mammals, by the elephant, rhinoceros, ta- 
pir, hippopotamus, zebra, quagga, giraffe, and camel. 

Marsupials, by the kangaroo. 

Birds are represented by the condor, ostrich, eagle, ibis, 
flamingo, cassowary, bird of paradise, peacock, and parrot. 

Reptiles are represented by the crocodile, alligator, 
iguana, and turtles. 

The temperate fauna, though characterized by fewer of 
the higher species of animals, yet contain many of large 
size, and among them animals of great use to man. 

In temperate fauna, the carnivorous mammalia are rep- 
resented by the lynx, hyena, wolf, jackal, dog, fox, rac- 
coon, bear, seal, and walrus. 

The herbivorous mammalia, by the wild boar, hog, 
horse, ass, ox, sheep, goat, chamois, moose, elk, reindeer, 
stag, antelope, buffalo, camel, and llama. 

The gnawing mammals, by the beaver, squirrel, rat, and 
porcupine. 

The whale, by the sperm and white whale. 

The marsupials, by the kangaroo. 

Birds, by the condor, vulture, hawk, eagle, owl, parrot, 
turkey, pheasant, wren, thrush, robin, nightingale, lark, 
pelican, and albatross. 

The arctic fauna contain but comparatively few large 
land species; the chief characteristics are numerous 
smaller furry species. 

The terrestrial arctic fauna are characterized by the fol- 
lowing animals : the white polar bear, the reindeer, the 
moose, and the musk-ox. 

The marine arctic fauna are characterized by the Green- 
land whale, the seal, and the walrus. The whale is among 
the largest species of the animal world. 

The peculiar distribution of the vegetation of the con- 
tinents produces corresponding peculiarities in their cha- 
racteristic fauna. 

The North American continent is characterized by the 
preponderance of its plant-eating mammals. The cause 
of this peculiarity is to be found in the abundance of its 
pasture lands. 

Fur-bearing animals particularly characterize the north- 
ern and central portions of North America. 

There are three natural districts of fur-bearing animals 
in North America: 1. The forest region; 2. The barren 
grounds; 3. The prairie regions. 

The South American continent is especially character- 
ized by the predominance of reptilian life, aquatic birds, 



and insects. The cause of the peculiarity is traceable to 
the predominance of the vegetable life over the animal. 

The Asiatic continent is especially characterized as 
being the original home of most of the animals which 
man has domesticated. The cause of this peculiarity is 
traceable to the fact that Asia was the primitive home of 
man himself. 

The great deserts of Africa are characterized by the 
presence of animals which are peculiarly noted for their 
swiftness of locomotion. 

In the remaining portions of Africa, the luxuriant vege- 
tation sustains animals of a larger, bulkier growth; as, for 
example, the elephant, rhinoceros, hippopotamus, and the 
giraffe. 

Australia is peculiarly characterized by the presence of 
the marsupials. It is the home of the kangaroo, the most 
important of the marsupials. 

Ethnography treats of the varieties of the human race, 
and their distribution. 

Man has a wider range of distribution than any other 
animal. 

It is believed by most that all the varieties of the hu- 
man race were originally descended from one family. 

Though greatly different in color, size, stature, and in- 
telligence, the general anatomical structure, the basis on 
which all other animals are classified, is invariably the 
same, even in the most widely differing races. 

The languages of Europe and of a large portion of Asia, 
appear to owe their origin to one parent nation, which 
dwelt, during pre-historle time, in the neighborhood of 
Mount Ararat and Mesopotamia. 

The primary races are the Caucasian, the Mongolian, 
and the Negro. 

The secondary races are modifications of the Mongolian : 
they are the Malay, the American, and the Australian. 

The Caucasian race inhabits South-western Asia, North- 
ern Africa, and nearly the whole of Europe. 

The Caucasian race may be divided into three branches : 
the Hamitie, the Semitic, and the Japhetic, or the Indo- 
Europeans. 

The Mongolian race inhabits all of Asia, except a small 
part of the Malay Peninsula and those portions of the 
continent occupied by the Caucasians. 

The Chinese, Japanese, Esquimaux, Lapps, Finns, Turks, 
and Magyars are the most important of the Mongolians. 

The Negro race inhabits all the continent of Africa not 
occupied by the Caucasians. 

The Malay race inhabits the southern part of the Malay 
Peninsula, Madagascar, and the islands of the Indian and 
Pacific Oceans. 

The Australian race inhabits all the continent of Aus- 
tralia not settled by the whites. 



REVIEW QUESTIONS. 



Define zoological geography. Fauna. 

Why should the distribution of heat and moisture form 
the true basis for the distribution of animal life? 

Distinguish between the horizontal and the vertical dis- 
tribution of animals. 

What difference exists between terrestrial tropical fauna 
and marine tropical fauna ? 

Between what limits, in the vertical distribution of ani- 



mals, do the fauna of a tropical mountain-range resemble 
that of the tropical horizontal zone? Of the temperate 
zone? 

What lines generally form the boundaries of animal 
regions? 

Which possesses the greater power of acclimation, man 
or the inferior animals? 

State the characteristics of the tropical fauna, naming 



140 



PHYSICAL GEOGRAPHY. 



the principal camivora, herbivora, cetacea, cheiroptera, 
marsupials, birds, and reptiles. 

State the characteristics of the temperate fauna, naming 
the principal camivora, herbivora, rodentia, cetacea, mar- 
supials, birds, and reptiles. 

State the characteristics of the arctic fauna, naming the 
characteristic terrestrial and marine species. 

What peculiarities characterize the fauna of North 
America? What is the cause of these peculiarities? 

What are the peculiarities of the fauna of the South 
American continent? What is the cause of these pecu- 
liarities? 

What is the main peculiarity of the Asiatic fauna ? 

Describe the districts of fur-bearing animals of North 
America. Of Asia. 

For what peculiarity are the animals of the deserts of 
Africa and Arabia noted ? 

What is the main characteristic of the Australian fauna ? 



Define ethnography. 

What arguments can be adduced to show the probable 
unity of the human race ? 

Name the primary races. 

Name the secondary races. 

Into what three branches may the Caucasian race be 
divided? 

What peoples have descended from the Aryans, or the 
Indo-Europeans ? 

Name the principal Celtic nations. 

What nations have sprung from the ancient Romans? 

What nations have descended from the Germans? 

Name the Slavonic nations. The Iranians. 

Name the parts of the world inhabited by each of the 
primary and secondary races. 

Describe the peculiarities of each of these races. 

Name a few of the peoples which belong to each of the 
races. 



MAP QUESTIONS. 



^K3»<0 



Trace on the map of the Vertical Distribution of Ani- 
mal Life, the characteristic fauna in those parts of each 
of the continents, lying between the level of the sea and 
5000 feet. Between 5000 and 10,000 feet. Between 10,000 
and 15,000 feet. Between 15,000 and 20,000 feet. 

Name from the map of the Distribution of Animals, the 
tropical species of the Americas. Of Africa. Of Asia. 
Of Australia. 

Name, in a similar manner, the temperate and arctic 
species of the Americas. Of Europe. Africa. Asia. Aus- 
tralia. 

In what portions of the world is the seal found ? The 
walrus ? The whale ? 

Trace on the map the southern limit of the polar bear. 
Of the reindeer. Of monkeys. Of the elephant and rhi- 
noceros. The northern limit of the camel. Of monkeys. 



Locate the chief districts of venomous serpents in the 
eastern and western hemispheres. 

Describe the region of the musk-ox. Of the grizzly 
bear. Of the buffalo. 

State, from the Ethnographic Map, the portions of the 
world inhabited by the Caucasian race. The Mongolian 
race. The Ethiopian race. The Malay race. The Amer- 
ican race. The Australian race. 

What different peoples dwell north of the arctic circle? 
South of the tropic of Capricorn ? 

Trace on the map the northern limit of permanent 
habitation. The southern limit. 

What race inhabits Hindostan ? What people ? What 
race inhabits Abyssinia? What people? Greenland? 
Patagonia? China? Mexico? France and Spain ? North- 
ern Norway and Sweden ? Arabia ? Madagascar ? 




MINERALS. 



141 



Section III. 



MINERALS. 



CHAPTER I. 

Minerals. 

368. General Distribution of Minerals. — The 
distribution of the various mineral substances 
that form parts of the earth's crust, unlike the 
distribution of the earth's plant and animal life, 
is independent of the distribution of heat and 
moisture. Mineral products, therefore, cannot be 
arranged in zones, according to latitude and alti- 
tude, as can the plants and animals. 

The absolute dependence of plants aDd animals on the 
distribution of heat and moisture necessarily limits them 
to those parts of the earth in which the requisite condi- 
tions exist. Moreover, while some animals, to a certain 
degree, possess the ability to become acclimated, that is, 
to accommodate themselves to changes in climate, yet 
they are necessarily limited to the regions in which the 
vegetable food exists on which they are directly or in- 
directly dependent. Mineral substances, on the contrary, 
are not, to any marked degree, dependent on existing cli- 
matic or surface conditions, since the conditions under 
which they were formed or deposited no longer exist. 

Since some mineral substances are practically limited 
to certain geological formations, a fairly good distribution 
might be based on the geological strata, were it not for 
the fact that, in many cases, through the agency of ero- 
sion, such substances have been distributed through the 
rocks of later formations. Moreover, in many cases, the 
mineral products are found in nearly all the geological 
formations. No attempt, therefore, will be made to 
arrange the earth's mineral products in characteristic 
zones or regions. 

369. Value of Mineral Products. — The civil- 
ization of man is largely dependent on the char- 
acter and extent of the earth's mineral products. 
His progress would have been seriously retarded 
had the earth contained no metallic substances 
from which he could fashion tools, build machines, 
form the rails for steam and electric roads, or the 
electric conductors for telegraph, telephone, elec- 
tric light and power lines, and had he no metals 
suitable for coining or for ornamentation. Had 
no stores of energy been placed in the earth's 
crust for his use, in beds of coal, in peat-bogs, or 
in recesses filled with coal-oil or natural gas, or 



did he fail to find among the earth's mineral 
treasures, beds of sandstone, granite, marble or 
other similar materials with which to build his 
houses, his ability to adapt himself to various 
climates would have been seriously restricted. 
Moreover, if the mineral products now employed 
for their medicinal or curative properties were 
denied to him, life and health would have been 
markedly decreased. 

370. Varieties of Mineral Substances. — Min- 
eral substances occur in a gaseous state, as in 
natural gas ; in the liquid state, as in petroleum 
or coal-oil ; and in the solid state, as in the 
various building stones, coal, rock-salt, and metal- 
lic ores generally. The solid state is by far the 
most common. Mineral substances occur at 
varying depths and are obtained by different 
mining processes. Sometimes, as in the case of 
gold, the mineral occurs near the surface, in beds 
of sand or gravel. Here, hydraulic milling, or the 
washing away of the deposits by powerful streams 
of water, may be adopted. Generally, however, 
the deposits occur at fairly considerable distances 
below the surface, in which case shaft-mining is 
necessary ; i. e., pits, shafts, or galleries are cut 
through the crust so as to reach the deposits. 

Building stones are generally obtained from 
open cuttings or quarries, since the cost of taking 
out such substances from great depths would be 
restrictive. It is generally believed that large 
and valuable metallic deposits exist at depths 
below which mining operations have, as yet, been 
carried on. 

371. Classification of Mineral Products. — For 
convenience of study, mineral products may be 
divided into the following classes : 

(1.) The metals and their ores. 
(2.) Coal, peat, coal-oil and natural gas. 
(3.) Clay, kaolin, marls, salt, sulphur and 
graphite. 

(4.) Building stones. 

(5.) Precious stones or gems. 

372. The Metals and their Ores. — The most 
important metals are gold, silver, platinum, iron, 



142 



PHYSICAL GEOGRAPHY. 



copper, tin, lead, zinc, mercury, nickel, antimony 
and aluminium. Gold, silver and platinum are 
sometimes called the precious metals. 

Metals occur either in the pure or native state 
or condition, uncombined with other substances ; 
in combination with other metals as alloys; or 
in combination with non-metallic substances as 
ores, such as oxides, sulphides, chlorides, carbon- 
ates, etc. 

Gold, silver, platinum and copper frequently 
occur in the native or metallic state or alloyed 
with other metals. 

373. Gold, the most valuable of the metals, 
does not readily rust or tarnish on exposure to 
air, and is extensively employed for coinage and 
jewelry. It occurs most extensively in the 
native or metallic state in small granules or 
irregular masses, called nuggets; in veins in quartz 
rocks ; in the sand or gravel of river beds ; or in 
alluvial deposits called placers. Native gold is 
found usually slightly alloyed with other metals. 

The deposits in the western parts of the United States 
are the richest in the world. Those of Australia, are, 
perhaps, next in importance. Mexico, Central America, 
South America, Alaska, Western and Southern Africa, 
New Zealand and portions of the regions adjoining the 
Ural Mountains, have also rich deposits. 

Perfectly pure gold is too soft to he employed for coins 
or jewelry. In order to render it sufficiently hard for use 
it is usually alloyed with silver or copper. 

374. Silver and Platinum. — Silver, like gold, is 
largely employed for coinage and for jewelry. It 
does not easily oxidize, but readily blackens on 
exposure to gases containing sulphur. Silver is a 
widely-distributed metal. It occurs sometimes in 
the native or pure state, but is usually either 
mixed or alloyed with other metals, or occurs as 
a sulphide. It is frequently associated with de- 
posits of copper, lead and other metals. 

The richest silver deposits in the United States are 
situated in the western parts, especially in Colorado and 
Nevada. Mexico and South America also have valuable 
deposits. 

Platinum, one of the heaviest metals known, 
occurs native and alloyed with other metals. It 
resembles silver in color. It is extensively em- 
ployed for the leading-in wires of incandescent 
electric lamps. Its exceedingly high melting 
point renders it especially fitted for use in the 
construction of small vessels, such as crucibles, or 
retorts, that are required to resist exposure to high 
temperatures. The principal deposits of platinum 
are in the region of the Ural Mountains. 



375. Iron, Copper, Tin, Lead, Zinc, Mercury, 
Nickel and Antimony. — These valuable metallic 
substances, with the exception of tin, are very 
generally distributed and rich deposits occur in 
all the continents. 

Iron occurs in vast deposits in nearly all parts 
of the world. Iron possesses a number of prop- 
erties which render it by far the most useful of 
all the metals. Pure or wrought iron, when 
softened by heat, can readilv be rolled into sheets 
or forged into any des : cd state. It may readily 
be drawn into wi" „. Its great tenacity renders it 
extremely valuable as a building material. When 
mixed with a small quantity of carbon, iron 
readily fuses and it may then be cast into any 
desired shape. Combined with a small quantity 
of carbon it forms the well-known substance, steel. 

Copper, so extensively employed in the electri- 
cal industries, possesses properties that give it a 
prominent place among the useful metals. It is 
malleable and ductile ; i. e., may readily be beaten 
or rolled out into sheets, or drawn out into wires. 
It forms a number of valuable alloys ; — such as 
brass with zinc ; and gun-metal and bronze, with 
tin. 

The deposits of native copper in the Lake Superior dis- 
tricts, in the United States, are the richest in the world. 

Zinc and Lead are valuable metals. Zinc is 
readily rolled into sheets, and is not readily oxid- 
ized or rusted. Galvanized iron, or iron covered 
with a layer of metallic zinc, resists oxidation. 
Lead is employed for water-piping, the lining of 
tanks, bullets, etc. It forms valuable alloys, and 
is largely employed in the production of paints. 

Extensive deposits of zinc and lead ores occur in Mis- 
souri and adjoining States in the United States. 

Tin is the well-known metal employed in tin- 
ware. Tin-plate consists of sheets of iron covered 
with a thin layer of tin by dipping them in a 
bath of molten tin. 

The principal ore of tin is the oxide. Valuable deposits 
occur in Cornwall, England ; in the Island of Banca ; and 
in Australia and Mexico. 

Mercury is distinguished from the ordinary 
metals by being liquid at ordinary temperatures. 
It is extensively employed in thermometers and 
barometers. Its power of forming alloys with gold 
and silver is utilized in the amalgamating process 
of extraction. An amalgam of mercury and tin 
is employed for the reflecting surfaces of mirrors. 

Valuable deposits of cinnabar, the red sulphide of mer- 
cury, occur at Almaden in Spain; in California; and in 
Asia Minor. 



MINERALS. 



143 



Nickel is a metal which does not readily tarnish. 
It is extensively employed for electroplating iron 
and other readily-oxidizable metals. It forms a 
number of valuable alloys, one of which is Ger- 
man silver. Nickel is employed to some extent in 
coinage. Antimony is a metal which when 
alloyed with lead is extensively employed as type- 
metal. This alloy possesses the property of tak- 
ing sharp casts, thus permitting the type to be 
readily made. Valuable deposits of its ore occur 
in the United States and in Europe. 

Aluminium is a remarkably light metal, ob- 
tained from clay. It is not oxidized by exposure 
to air, and possesses valuable properties. 

376. Coal, Peat, Coal-oil and Natural Gas form 
a group of natural fuels of great use to man. 

Coal is by far the most important of the 
natural fuels. Its formation is practically limited 
to the carboniferous age. (See paragraph 75.) 

Valuable deposits of coal are found in nearly all parts 
of the world. The deposits of the United States are prob- 
ably richer than in any other country. (See paragraph 
417.) 

Peat, an inferior form of fuel, is a carbonaceous deposit 
that occurs in marshy districts in moist climates. Exten- 
sive peat-bogs exist in Ireland and in the United States. 

Coal-oil or petroleum, a valuable form of natural fuel, 
exists in reservoirs, as already described in paragraph 167. 
Valuable oil-fields exist in Western Pennsylvania ; in Bus- 
sia ; and in other parts of the earth. 

Natural gas exists in great quantities in the neighbor- 
hood of the coal-oil districts in the United States and 
elsewhere. (See paragraph 420.) 

377. Clay, Kaolin, Marl, Salt, Sulphur and 
Graphite. — Besides the mineral products already 
described there is a great variety of others that 
are employed for various purposes in the arts or 
sciences. Some of the more important of them 
are clay, kaolin, marl, salt, sulphur and graphite. 

Clay and kaolin are extensively employed in the 
manufacture of bricks, pottery, terra-cotta ware, stone- 
ware, china and porcelain. Marls are various mixtures 
of clay and lime, and are employed for fertilizing lands. 
Clay and marls are extensively found in all parts of the 
earth. Common salt, or chloride of sodium, is one of the 
principal saline ingredients in ocean water, and in the 
waters of inland seas or steppe lakes. It occurs also in 
vast deposits as rock-salt where it has been derived from 
the gradual evaporation of saline waters. Various saline 
or salt springs exist. (See paragraph 166.) 

Sulphur exists in a native or pure state in volcanic dis- 
tricts, or combined with various metallic substances as 
sulphides, it is generally distributed. It is extensively 
employed in the manufacture of sulphuric acid. 

Graphite is a form of carbon extensively employed in 
lead pencils, and is valuable as a lubricant. 

In addition to the above mineral products are beds of 
sand, suitable, when mixed with burnt lime, to form mor- 



tars and cements ; or to form glass, when fused with 
potash or other basic substances. 

378. Building Stones are found in immense 
deposits near the surface in various parts of the 
earth. A material to be suitable for building 
purposes must possess marked strength and tena- 
city and be able to resist being crushed by the 
weight placed upon it. It must especially resist 
disintegration or breaking up under the action 
of the weather. 

The more important building stones are granite, 
gneiss, blue-stone, sandstone, magnesian lime- 
stone, marble and slate. 

379. The Precious Stones or Gems. — Besides 
the mineral substances already referred to, which 
with some few exceptions occur in extensive 
deposits in nearly all parts of the world, there 
are others which either occur very rarely, or, if 
common, are but seldom found in fine specimens, 
free from flaws or other blemishes. These min- 
erals are called the precious stones or gems, and 
are highly prized as articles of jewelry. 

The principal precious stones, or gems, are the 
diamond, the sapphire, the ruby, the topaz, the 
emerald, the beryl, the opal, and the garnet. 

The diamond is a crystallized form of pure carbon. Its 
value depends on its lustre and color, on its freedom from 
flaws, and on its size, especially the latter. In the natural 
state it is generally lustreless and requires to be cut and 
polished in order to bring out its fire or lustre. Its value 
is rated by the carat (approximately 3 grains). 

The principal diamond-fields of the world are in South 
Africa, New South Wales, the Ural Mountains and Brazil. 

The sapphire is a beautiful blue stone; the best speci- 
mens are found in Brazil. The ruby has a deep red color ; 
perfect specimens of more than two carats in weight are 
more valuable than the diamond ; the best specimens are 
found in Siam. The topaz is a yellow stone of various 
shades ; the best specimens are found on Topaz Island in 
the Bed Sea. The emerald is a gem of a beautiful green 
color; the finest specimens are found in New Granada. 
The beryl is a stone which occurs in the form of six-sided 
prisms, usually either blue, green, or yellow, but some- 
times colorless. The opal, with its changing hues and 
blending colors, has a strange beauty which defies imita- 
tion. The garnet occurs in a variety of colors and is quite 
abundant, being found in all the continents. 

Other minerals used for ornamentation and jewelry, but 
less valuable than the above, are turquoise, lapis-lazuli, 
malachite and quartz. 

Quartz is a crystal stone of some beauty; amethyst, 
cat's-eye, chalcedony, onyx, sardonyx, carnelian, jasper, 
agate, blood-stone, plasma, and chrysoprase are varieties 
of quartz of different colors and markings. 

Pearls are deposits of carbonate of lime and organic 
matter; they are found within the shells of the pearl 
oyster and other mollusks ; they occur on the tropical 
coasts of Asia and America, the best specimens are found 
on the coasts of Ceylon. 



144 



PHYSICAL GEOGRAPHY. 



SYLLABUS. 



oXWo 



The earth's mineral products cannot be arranged in 
zones according to the altitude or latitude as can its plants 
and animals. 

The civilization of man is largely dependent on the 
character of the earth's mineral products. 

Mineral substances occur either in the gaseous, the 
liquid or the solid state; the last is by far the most 
common. 

The earth's mineral products may be conveniently 
grouped under the following classes : — namely, (1) Metals 
and their ores. (2) Coal, peat, coal-oil and natural gas. 
(3) Clay, kaolin, marl, salt, sulphur and graphite. (4) 
Building stones. (5) The precious stones or gems. 



The most important metals are gold, silver, platinum, 
iron, copper, tin, lead, zinc, mercury, nickel, antimony 
and aluminium. Gold, silver and platinum are sometimes 
called the precious metals. 

The principal natural fuels are coal, peat, coal-oil and 
natural gas. 

Clay, kaolin, marl, salt, sulphur and graphite are ex- 
tensively employed in the arts. 

The principal building stones are granite, gneiss, blue- 
stone, sandstone, magnesian limestone, marble and slate. 

The principal precious stones or gems are the diamond, 
the sapphire, the ruby, the emerald, the beryl, the topaz, 
the opal, and the garnet. 



REVIEW QUESTIONS. 



Why cannot the earth's mineral products be readily 
arranged in characteristic zones or regions? 

In what manner is man's progress dependent on the 
character and distribution of mineral products. 

In what different states or conditions do the earth's 
mineral products occur? Which of these is the most 
common ? 

How may the earth's mineral products be classified ? 

Name the precious metals. Name some of the most im- 
portant of the more common metals. 



Name any five common metals, and some practical uses 
to which each may be put. 

Name the principal natural fuels. 

For what purposes are clays and kaolins employed ? 
What are marls? Name some of the principal sources of 
common salt. 

Name the principal building stones. 

What are diamonds ? Where are they found ? How is 
their value estimated? Upon what does it depend? 

Name some other precious stones. 



*'U* 




Page 145. 




Part VI. 



THE PHYSICAL FEATURES OF THE UNITED STATES. 




The civilization and development of a country are dependent, in a marked degree, on the pecu- 
liarities of its physical features. The soil and climate exert their influence on the vegetable and animal 
life, and these, in turn, react on man. If proper soil and climate exist ; if the peculiarities of the 
surface structure permit of ready intercommunication, and if extensive deposits of coal and valuable 
metals occur, the future development of the country is assured. 

The physical features of the magnificent domain of the United States are such as seem to destine it to 
become the theatre of the civilization of the future. The peculiarities of its position and extent, the 
nature of its soil, the climate, and rainfall, the size and constancy of its navigable rivers, and the extent 
and variety of its valuable mineral deposits, eminently fit it to sustain a very high order of civilization. 



CHAPTER I. 

Surface Structure of the United 
States, exclusive of Alaska. 

380. Situation and Extent. — The United States 
occupies the entire breadth of the North American 
continent, between lat. 49° N., and 24° 30' K and 
extends from long. 66° 50' W. from Greenwich, to 
124° 31' "W. The total area, exclusive of Alaska, 
is 3,026,500 square miles. 
146 



381. Coast Line. — The coast line is compara- 
tively simple and unbroken. On the east, the 
Atlantic Ocean extends into the land in three 
wide curves; on the south, is the deep indenta- 
tion of the Mexican Gulf; on the west, the land is 
thrust out into the Pacific in an almost unbroken 
curve. The total coast line, exclusive of the ad- 
joining islands and Alaska, is about 12,609 miles. 

382. Gulfs and Bays. — The principal indenta- 
tions on the eastern coast are Long Island Sound, 
Delaware and Chesapeake Bays, and Albemarle 



SURFACE STRUCTURE OF THE UNITED STATES. 



147 



and Pamlico Sounds. On the western coast are 
the Gulf of Georgia and the fine harbor of the 
Bay of San Francisco. 

The Atlantic shores slope gently toward the 
ocean ; the Pacific shores are abrupt. 

383. Islands. — The islands of the Atlantic coast 
are of three distinct classes : those north of Cape 
Cod are, for the most part, rocky, and are de- 
tached portions of the mainland ; those south of 
Cape Cod are generally low and sandy, and are, 
for the most part, of fiuvio-marine formation ; those 
off the coast of Florida are of mangrove forma- 
tion. On the Pacific coast are the Santa Barbara 
Islands, a rocky group south-west of California; 
and Vancouver Island, north-west of Washing-ton. 




Fig. 123. View on the Coast of Monnt Desert Island, Maine. 

384. Mangrove Islands. — Mangrove trees grow 
in dense jungles, on low muddy shores, in tropical 
regions. From both trunks and branches the 
trees throw out air-roots, which spread so as to 
cover the adjoining spaces in an almost intermin- 
able network of roots and branches. The area of 
surface covered by the trees is still further in- 
creased by the curious property which the seeds 
possess of sprouting while ou the tree, subse- 
quently floating away, and afterward affixing 
themselves to the bottom of the jungle, to form 
new growths. In this way, the trees form man- 
grove islands, which at first are not true islands, 
the trees simply standing above the water by 
means of their intertwined roots. In course of 
time, however, sediment, collecting between the 
roots of the trees, forms islands. These islands 
are common in the shallow water off the coasts 
of Florida. 

385. Coral Reefs of Florida. — The peninsula 
of Florida, south of the northern extremity of the 
Everglades, and probably as far north on the 

17 



eastern coast as St. Augustine, is, according to 
Agassiz, a species of coral formation, formed, 
however, under different conditions than are the 
coral islands of the Pacific. 




Fig. 124. Florida Eeefs and Keys, (LeConte.) 




Fig. 125. Everglades, Reefs, and Keys of Florida. (LeConte.) 

Figure 124 is a map of Florida with its reefs and keys. 
Figure 125, is a section along the line A. A. In Fig. 124 
the line a a, shows what was at one time the limit of the 
southern coast of Florida, b b, is the present limit of the 
southern coast, c c, are the keys, which are low islands. 
d d, is the growing coral reef, e, is the Everglades, dotted 
with islands, called hummocks. Between cc, and d d, is 
the ship channel. Outside the growing coral reef dd, are 
the profound depths of the Gulf Stream G. S. 

The growth of the reef-formations is explained by 
LeConte as follows (Fig. 125) : a, was at one time the limit 
of the southern coast of Florida. 6, is the present southern 
coast, which at one time was a coral reef like d. Upon b, 
a line of coral islands gradually formed connecting it 
with the old southern coast a. The ship channel between 
a, and b, gradually filled up and formed the Everglades e. 
Meanwhile, another reef formed, in the position of the 
present keys, c, the ship channel being between b, and c. 
This reef has now grown to be a line of coral islands, 
and the ship channel, between 6, and c, converted into 
shoals and mud flats, /. The present ship channel is 
between c, and d. In course of time the southern coast 
will extend to the present line of keys, c, and the shoal 
water /, will become another Everglades. Outside the 
present keys c, another coral reef d, is growing, to which 
the coast will ultimately extend, and which will mark 
the limit of the formation, owing to the deep waters 



148 



PHYSICAL GEOGRAPHY. 



of the Gulf Stream, immediately beyond it. In Figure 
125, the dotted lines show the successive steps of the 
formation. 

386. Forms of Belief.— The United States is 
traversed by two distinct mountain-systems : the 
Pacific System — the predominant system — on the 
west, and the Appalachian System — the secondary 
system — on the east. 

387. The Pacific System, consists of a broad 
plateau, traversed by two distinct mountain-sys- 
tems : the Pocky Mountains, and the Pacific 
mountain-chains. It embraces about one-third 
of the entire territory of the United States 
proper. 

388. The Rocky Mountain System, consists of 
a number of parallel chains connected by numer- 
ous cross ranges. They rise from the summits of 
an elevated plateau, which in some places is fully 
7000 feet above the sea. The chains are broken 
in several places by transverse valleys or passes, 
traversed by important rivers. The most import- 
ant of these passes is South Pass, in Wyoming, 
traversed by the Sweet Water River, a tributary 
of the Platte. The Missouri, Rio Grande, and 
other rivers also flow through similar depressions. 

The chains are separated into northern and southern 
sections by a gap occupied by an elevated plateau, over 
which the Union Pacific Eailroad passes. 

Among the many lofty peaks of this mountain- 
system are Long's Peak, 14,050 feet ; Pike's Peak, 
14,216 feet ; and Fremont's Peak, 13,570 feet high. 

A remarkable feature of these mountains is the basin- 
shaped valleys, called parks, formed by transverse ranges 
connecting the parallel ranges. The most important of 
these parks are North, South, and Middle Parks. They 
are nearly rectangular in outline, and are hemmed in by 
huge mountain-ranges. Each park gives rise to an im- 
portant river. The rich verdure of these deeply-sunken 
basins is rendered the more striking by contrast with the 
desolate mountains surrounding them. 

The Yellowstone National Park, in the north-western 
part of Wyoming, is traversed by some of the head-waters 
of the Yellowstone Eiver. It is a region of hot springs, 
deep gorges, high mountain-peaks, and magnificent scenery. 
It has been set apart by the government for the purposes of 
a public park. 

The Great Plains, an elevated plateau, lie 
along the eastern side of the Rocky Mountains. 
They are undulating plains, which slope by 
almost imperceptible gradations, to the valley 
of the Mississippi. They are treeless, and near 
the base of the mountains have but a scanty 
vegetation. Near the lower part of the slope 
they merge into prairies, covered with a luxuri- 
ant growth of grass. 



389. The Pacific Mountain-Chains extend 
through California, Oregon, and Washington, 
and, in general, are parallel to the Rocky Moun- 
tains. They comprise the Cascade Mountains in 
Oregon and Washington, and the Sierra Nevada 
and the Coast Mountains in California. 

The famous gold regions of California lie mainly west 
of the Sierra Nevada and the Coast Mountains. 

The loftiest peaks of the Pacific Mountain- 
chain exceed those of the Rocky Mountains in 
height. The highest peaks are Mt. Rainier in 
the Cascade Range, 14,444 feet high ; and in the 
Sierra Nevada Range, Mt. Shasta, 14,482 feet 
high, and Mt. Whitney, 14,800 feet high. 

The culminating point of the Pacific Mountain- 
chains is Mount St. Elias, in Alaska, which is es- 
timated to be 19,500 feet high. 

The Cascade Mountains contain numerous ex- 
tinct volcanoes. 

The Great Basin lies between the Wahsatch on the east, 
and the Sierra Nevada and Cascade ranges on the west, 




Fig. 126. The Great CaSon of Colorado. 

It possesses a true inland drainage. East of the Wahsatch 
Mountains and the western flanks of the elevated peaks 



SURFACE STRUCTURE OF THE UNITED STATES. 



149 



and ranges of Colorado, lies a region drained by the head- 
waters of the Colorado. This region, together with the 
country lying in the middle courses of the river, is a won- 
derful section of country, traversed by streams that have 
eroded their valleys and flow through deep canons, some 
of which are over 6000 feet deep. A view of a part of one 
of the most noted of these cafions is shown in Fig. 126. 

390. The Appalachian System, sometimes called 
the Alleghany Mountains, extends from Georgia 
to Maine, nearly parallel to the Atlantic. The 
chain varies in breadth from 150 to 200 miles. 
The system consists of an elevated plateau, 
bearing several mountain-chains, separated by 
wide valleys. In the northern and southern 
parts of the chain, where the elevation is the 
greatest, the system is formed of irregular groups, 
without any definite direction. In the centre, 
low parallel chains occur separated by fertile val- 
leys. These valleys generally take the names of 
the rivers which flow through them. 

The system is highest in North Carolina, where 
Mt. Mitchell, 6707 feet high, forms its culminat- 
ing point. 

Beginning in the north, the system includes the 
White fountains in New Hampshire, with Mount 




Fig, 127. The Natural Bridge (Virginia). 

Washington, 6294 feet high ; the Green Mountains, 
in Vermont ; the Adirondacks, in New York, with 



the culminating peak of Mount Marcy, 5379 feet 
high ; the Catskill Mountains, the Blue Mountains, 
the Alleghanies, the Blue Ridge, the Cumberland 
Mountains, and others. 

The Natural Bridge, in Eockbridge County, Virginia, 
is, from its peculiar formation, an object of interest to 
tourists. 

391. Plains. — There are two great low plains 
in the United States: the Atlantic Coast Plain 
and the Plain of the Mississippi Valley. 

The Atlantic Coast Plain lies along the eastern 
flanks of the Appalachian Mountains. It varies 
in width from 50 to 250 miles. Along the coast 
the soil is comparatively sandy, and has been 
formed by the combined action of the rivers and 
ocean. 

The extensive swamps which occur in this region — such 
as Cypress Swamp, in Delaware, Dismal Swamp, north of 
Albemarle Sound, Alligator Swamp, between Albemarle 
and Pamlico Sounds, and Okeflnokee Swamp, in Southern 
Georgia — are of fluvio-marine origin. The Everglades, in 
Florida, are the result of a coral formation. Farther from 
the coast, the plain is more elevated ; long valleys occur, 
which are very fertile, particularly near the river bottoms. 

The Mississippi Valley lies between the predomi- 
nant and the secondary mountain-systems. It is 
over 300,000 square miles in area, and includes 
some of the most fertile land in the country. 
Much of it is covered with forests or prairies. 

392. River- and Lake-Systems. — The United 
States is particularly noted for the number and 
extent of its navigable rivers. 

Oceanic Drainage — Atlantic System. —Among 
the important rivers emptying directly into the 
Atlantic Ocean are the Penobscot, Merrimac, 
Connecticut, Hudson, Delaware, Susquehanna, 




Kg, 128, Scene on the Mississippi. 

Roanoke, Cape Fear, Santee, Savannah, Altar 
maha, and the St. John's. 



150 



PHYSICAL GEOGRAPHY. 



Of the rivers flowing into the Mexican Gulf, 
the Appalachicola, Alabama, Mississippi, Sabine, 
Trinity, Brazos, Colorado, and the Rio Grande are 
the most important. 

The Mississippi, taking its origin in the head-waters of 
the Missouri — which is the true parent stream — is the long- 
est river in the world, its length being 4490 miles. Its 
tributaries are, in general, navigable for great distances, 
and thus afford ready communication with different parts 
of the basin. The important tributaries of the Mississippi 
on the west are the Minnesota, the Missouri, the Arkansas, 
and the Eed. On the east, the Wisconsin, the Illinois, and 
the Ohio. 

The Pacific System. — The principal rivers emp- 
tying into the Pacific Ocean are the Columbia, 
Sacramento, San Joaquin, and the Colorado. 

393. Inland Drainage. — The rivers and lakes 
of the Great Basin have no outlet to the ocean, 
and therefore form true steppe systems. Great 
Salt and Humboldt lakes are the principal lakes, 
and the Humboldt and the Reese, the principal 
rivers. 

There are two regions in the United States below the 
mean level of the sea: 

(1.) In the southern part of California, in Soda Valley, 
200 feet below the sea. 

(2.) Death Valley in Eastern California. These regions 
are extremely arid. 

394, Lake-Systems. — The most important lake- 
system of the United States lies in the northern 
part. It includes, among numerous others, five 
of the largest fresh-water lakes in the world : 
Superior, Michigan, Huron, Erie, and Ontario. 
From their immense extent, they resemble great 
inland seas. 

Numerous flmiatile or river lakes occur near the borders 
of the middle and lower courses of the Mississippi and its 
tributaries. They are nearly all found in the States west 
of the Mississippi. 

~**;°« 

CHAPTER II. 
Meteorology. 

395. Climate. — -The United States, exclusive of 
Alaska, lies entirely within the limits of the mathe- 
matical north temperate zone- 
Physical Zones. — As regards the actual distri- 
bution of heat, the United States lies between 
the annual isothermal lines of 40° and 77° Fahr. 
Its territory therefore embraces two zones of phys- 
ical climate, the physical north temperate and the 
physical torrid zones. The isotherm of 70°, the 
boundary of the physical torrid zone, 



through Florida, Louisiana, Texas, and Arizona. 
All of the country south of this line lies in the 
physical torrid zone ; all north of it, in the 
physical north temperate zone. 

The Territory of Alaska lies in the north frigid 
and north temperate zones. 

396. Mean Annual Isotherms. — The following pecu- 
liarities in the mean annual distribution of heat, will be 
seen from a study of the mean annual isotherms on the 
map (page 145) : 

The isotherm of 40°, the lowest mean annual tempera- 
ture, is found in a few elevated districts in New England, 
in the elevated districts around Lake Superior, and in the 
higher plateaus of the Eocky Mountains. 

The isotherm of 45°, east of the Mississippi, runs slightly 
north of the 44° of N. lat., and, except in New York, Ver- 
mont, and New Hampshire, is nearly parallel with it. In 
the Dakotas it bends toward the north-west, reaching 
the northern boundary of the United States in Mon- 
tana, when it bends suddenly toward the south-east, until 
it reaches Central Colorado, where, nearly parallel with 
its southward deflection, it again turns abruptly to the 
north. 

The isotherm of 50° is nearly parallel with the 41° N. 
lat., until it reaches Colorado, when it bends sharply south 
to the 36° lat. ; then it extends in a nearly direct line 
toward the north-west, enteriug the Pacific coast some- 
what to the north of Washington. 

The isotherm of 55° enters the Atlantic coast at lat. 40° ; 
it then extends south-west to Tennessee; thence north- 
ward to Kentucky, from which its course is nearly due 
west to Indian Territory, when it bends southward to 
about lat. 34° in New Mexico. From this point it extends 
in a nearly direct north-westerly course to lat. 41° in 
Northern California, when it bends sharply to the south, 
entering the Pacific Ocean at about lat. 36°. 

The isotherm of 52.5°, traced only on the western half 
of the map, starts from the north-western part of New 
Mexico, and runs in a nearly direct north-westerly course 
to North-eastern Nevada, when it divides, the northern 
branch extending to the north-western extremity of 
Washington, and the southern entering the Pacific in 
the neighborhood of San Francisco. 

The isotherm of 60° enters the Atlantic coast at Norfolk, 
Virginia ; it then trends south-west to Northern Georgia, 
from which its course is nearly due west until it reaches 
Indian Territory, when it runs south-west to New Mexico. 
Here it divides into two branches : the northern extends 
in irregular curves to lat. 40° in California, when it bends 
sharply to the south-east, entering the Pacific at about lat. 
34°. The southern branch enters the Gulf of California 
at about lat. 25°. 

The isotherm of 70° extends through Northern Florida. 
Southern Louisiana, and Texas. 

The isotherm of 75° extends through Southern Florida. 

397. Climatic Contrasts. — There is a marked 
contrast between the climate of the eastern and 
western coasts of the United States. The eastern 
coast is colder than the western. 

The difference in temperature is greater in the 
north ; the mean annual temperature of the coast, 
between New Jersev and Maine, is from 52° to 



METEOROLOGY. 



151 



42° Fahr., while on the shores of California, 
Oregon, and Washington, the mean is nowhere 
lower than 52°, and in many places is much 
higher. 

In the southern portions of the eastern and 
western coasts, the contrast is not so decided, 
owing to the peculiarly cool summers in the west- 
ern part of the continent. 

The Atlantic seaboard is much colder than corresponding 
latitudes on the western coasts of Europe. For example, 
the latitude of New York City is about the same as that 
of Madrid, Naples, and Constantinople; of Boston, the. 
same as that of Eome ; of Portland, Maine, the same as 
that of Marseilles; of Quebec, nearly that of Paris; and 
yet what a striking difference in their climates ! 

The western shores of America are, however, quite as 
warm as those of Europe. Sitka, in lat. 57°, has a winter 
mean very nearly the same as that of Edinburgh, in the 
same latitude. 

The higher mean annual temperature of the western 
coasts over that of the eastern will prove of great signifi- 
cance in the future history of the United States, since our 
western shores will admit of cultivation and settlement for 
a much greater distance north than will the eastern. " The 
difference," says Blodget, " covers 12° to 15° of latitude on 
the coast of the Pacific, and from 5° to 40° on the plains 
east of the Eocky Mountains. 

The sharp contrast between the climate of the 
eastern and western shores is caused by the at- 
mospheric and oceanic circulation, which, in both 
cases, is from west to east; hence, the higher tem- 
perature of the western shores, on account of the 
warm, vapor-laden winds from the Pacific, the 
comparatively heavy rainfall, and the warm ocean 
currents. The cold Arctic current, which comes 
from Baffin Bay down the Atlantic seaboard, 
reduces the mean annual temperature of the 
eastern coast. 

On the south, the Gulf Stream, emerging from 
between Florida and Cuba, tends to raise the tem- 
perature of the southern portions of the seaboard, 
though its greatest influence is exerted on the dis- 
tant shores of Europe. On the Pacific coast, the 
Japan current, after leaving the Asiatic shores, 
flows southward along the North American coasts, 
bathing them with its highly heated waters. 

398. Constancy of the Climate. — From obser- 
vations extending back as far as the year 1738, it 
appears, that from that time, the climate of the 
United States has undergone no decided change. 

399. Distribution of Wind and Kain.— The 
United States lie in the zone of the variable 
winds. Westerly winds, therefore, predominate. 

400. Precipitations. — The domain of the 
United States is well watered, copious rains fall- 
ing over nearly all portions of the surface, espe- 



cially on those which lie east of the predominant 
mountain-system. 

East of the 100th meridian from Greenwich, 
an average of at least 40 inches, or 3J feet, falls 
throughout the year. From this large rainfall, 
it is evident that the evaporation, which supplies 
the winds with moisture, must take place in the 
equatorial regions, and that, in general, the upper 
currents of equatorial winds bring the rain. The 
open sweep afforded to the winds by the Gulf of 
Mexico and the Mississippi Valley, increases the 
rainfall of the Gulf States. 

The heaviest annual rainfall is 65 inches, and 
occurs near the borders of the Gulf States, and 
along the Pacific seaboard in Washington and 
Oregon. Along the Atlantic border, it varies 
from 40 to 45 inches ; in the upper half of the 
Mississippi Valley, it varies from 25 to 40 inches ; 
in the lower half, from 40 to 65 inches ; in the 
upper course of the Missouri and the region of 
the Yellowstone, from 20 to 22 inches ; in por- 
tions of the Great Basin the rainfall is very 
limited, being but from 5 to 10 inches. 

As regards its distribution in time, rain is pos- 
sible at all seasons of the year over most of the 
country ; over some portions, however, it is peri- 
odical in character, these districts having a rainy 
and a dry season. 

East of the Mississippi River, rain may fall at 
any time of the year. Near the Atlantic coast, 
rain is especially abundant in the spring. 

West of the Mississippi the rainfall is more 
irregular. In Washington, on the Pacific coast, 
rain may fall at any time during the year. 
On other parts of the Pacific coast, rain is most 
frequent in winter ; during the summer, it is 
either scanty or wholly absent. This periodicity 
in the distribution occurs mainly in the region 
near the coast. In the interior, the precipitation 
is more irregular. 

401. The Weather Bureau. — Considerable light 
has been thrown on the meteorological conditions 
of the United States by the operations of the 
"Weather Bureau." 

The Weather Bureau was established by an 
Act of Congress in February, 1870, authorizing 
the Secretary of War to establish and equip 
stations in different parts of the country, where 
such simultaneous observations of the meteor- 
ological conditions of the atmosphere could be 
taken, as would enable the Department to give 
timely notice to all important ports on the Atlantic 



B152. WEATHER MAP, SHOWING CONDITION OF THE WEATHER ON A CERTAIN DAYIN APRIL. 





WEATHER SIGNALS. 



\Himfianiur 



FdirJvcatfter Signal 




Rain 
orSnoir 




Cold Warmer 

Wart FairWiathtr J a % „ 

followed InJt% hv 

or Snow 




ColdWavt 



STORM SIGNALS. 



V 



^p- 



MiTwirids. SJtwinds. IfE.winiis. SFwitvl?. 
CAUTIONARY SIGNALS. 



MfTmnds. SWmrula XK.windx. SEwmds. 



INFORMATION SIGNAL. 



METEOROLOGY. 



153 



coast and Great Lakes of the approach of danger- 
ous storms, and to collect such information as 
would be of value to shipping and other interests. 

In 1890, the direction of the Weather Bureau was, by 
Act of Congress, taken from the War Department and 
transferred to the Department of Agriculture. 

There are about 500 stations established by 
the Weather Bureau in different sections of 
the United States. At these stations there are 
trained and intelligent observers, who several 
times each day are simultaneously required to 
make careful observations of the temperature, 
humidity, and pressure of the air, the direction 
and force of the wind, the clearness or cloudiness 
of the sky, and the amount of rain or snow that 
has fallen during a given time. 

These observations are telegraphed to the Cen- 
tral Office at Washington, so that the Bureau is 
enabled to see the actual meteorological condi- 
tions which exist throughout the country at any 
given time, and from such knowledge, guided by 
previous experience, to prepare "synopses" of 
the weather and " indications," or forecasts. 

For the preparation of the "indications" the officer in 
charge prepares a number of graphic charts, based on the 
various data telegraphed to the Central Office, as the result 
of the simultaneous observations at the different stations. 
These charts exhibit the actual meteorological conditions 
that then exist, those that existed during the previous 
eight hours, and the previous twenty-four hours, and the 
conditions normal for the place at that particular time of 
the year. The data shown on these charts include the 
temperature, barometric pressure, humidity of the air, 
precipitation, condition of sky, force and direction of 
wind, etc. The " indications " are telegraphed to the press 
throughout the country. In general about 85 per cent, of 
these indications are verified. 

It should be borne in mind, in considering this very 
large percentage of verified forecasts, that the indications 
are predicted for extended areas, and, therefore, although 
the change may not have occurred in some limited section 
of the predicted area, it may have occurred in nearly all 
the other portions of the region. 

Changes in the Weather — Passage of a Great 
Storm. — Since nearly all the great storms of the 
United States are species of cyclones, that move 
over the country in a general easterly direction, 
when such a storm is once started it is not a dif- 
ficult matter to predict its general path, and thus 
foretell coming changes in the weather. 

The principal elements of uncertainty are the exact path 
in which the storm will move over the country, and the 
velocity of such motion. These the bureau can predict, 
approximately, from a comparison of all the previous 
storms of which it has records. 

The whirling direction of the wind in the Northern 
Hemisphere is in the opposite direction to that of the 



hands of a watch. Therefore, as the eastern side of a 
storm approaches any section of country, the winds blow 
generally from the south toward the north. The approach 
of a cyclone is generally attended by a fall of rain or snow. 
As the cyclone moves onward, and its western side passes 
over any locality, the general direction of the wind is 
from the north to the south. The passing of the cyclone 
is generally attended by clearing, cooler weather. 

Cold Waves. — On the edges of a cyclone the 
barometer is high. When one .storm follows an- 
other at a short interval, the area of high ba- 
rometer between them causes the wind to blow in 
all directions from the centre of high barometer, 
and a cyclonic movement of the air is thus es- 
tablished, possessing a progressive motion like a 
true cyclone. Since the direction of rotation of 
such a storm is opposite to that of a cyclone, it 
is called an anti-cyclone. Cold waves generally 
originate in anti-cyclones. 

The Weather Signals consist of signal-flags 
designed to indicate the probable weather and 
temperature of the coming day. 

The temperature signal indicates warmer weather when 
placed above the other flags, and colder weather when 
placed below them. The cold-wave flag indicates a de- 
cided fall in temperature. 

The Storm Signals are displayed at all ports on 
the Great Lakes or the Atlantic seaboard whenever 
it is considered probable that within twelve hours 
there will be experienced at those ports, or within 
one hundred miles thereof, a wind dangerous to 
navigation. The information signal is intended 
to notify ship-masters that, on application to the 
local observer, information will be given them 
relative to an approaching storm, which it is 
thought will be dangerous to vessels about to 
sail to certain ports. The cautionary signal is 
displayed on the Lakes only, when the vvinds 
expected will be severe, but not dangerous to 
well-equipped vessels. 

To reach the different cities, towns, and villages, and the 
hamlets of the rural districts, the indications, or forecasts, 
are telegraphed every midnight from the Central Office to 
centres of distribution, situated in different States. These 
reports are at once printed at each of these distributing 
stations, enclosed in envelopes, and forwarded to every 
post-office which can be reached by the swiftest mail 
facilities by 2 p.m. of the next day. Great benefit is 
thus conferred on agricultural interests. 

Warnings of coming floods, movements of river ice, 
sudden or unusual change of level in rivers, are also given 
as the occasion warrants. The warning is given whenever 
the water rises above a certain level, called the danger level. 

Another series of reports are for the benefit of internal 
navigation. They consist in the announcement, from day 
to day, of such changes of temperature for different sec- 
tions of the country as would be likely either to stop 
navigation by the freezing of the canals, or temporarily 



154 



PHYSICAL GEOGRAPHY. 



to open them sufficiently to enable ice-bound vessels to be 
pressed forward to the termini of the canals. . 

The value of the Weather Bureau can scarcely be over- 
estimated; the saving of shipping effected by the timely 
warning of a single severe storm may more than pay the 
entire expenses of the bureau for a large portion of the 
year. We append the following resume of the work of 
the bureau : 

(1.) The announcement of probable weather changes by 
the publication of " indications." 

(2.) The timely warning of the approach of severe 
storms. 

(3). The display of signals indicating coming changes in 
the weather. 

(4). The publication of farmers' bulletins. 

(5.) The river and canal reports. 

(6.) The display of symbol-maps, showing the actual 
state of the weather throughout the entire country. 

(7.) The publication of daily weather maps, monthly 
charts, and charts which give the results of the observa- 
tions of years. 

(8.) The publication of cotton-region reports, embracing 
reports of rainfall and maximum and minimum tempera- 
ture throughout the cotton districts from April 1 to 
October 31. 

The International Weather Service. — The suc- 
cess of the meteorological observations of the U. S. 
Weather Bureau has led to the establishment of 
stations for simultaneous observations over a large 
portion of the northern hemisphere and some sta- 
tions in the southern hemisphere. By simulta- 
neous observations of the meteorological conditions 
of the whole earth, many things yet unknown as to 
weather predictions are likely to be discovered. 

Tornadoes resemble cyclones in that they are 
whirling motions of the air. The area over 




Fig, 129. A Tornado. 

which they extend is more limited, but the 
velocity of the wind is higher than in cyclones, 
and, therefore, their destructive power is very 



great. When they pass over any section of 
country they leave devastation and ruin in their 
track. 

Tornadoes are of frequent occurrence in the 
central and western portions of the Mississippi 
Valley. 

Tornadoes have their origin in a rotary motion 
imparted to a mass of warm moist air that is 
temporarily imprisoned below a mass of colder 
air. The whirling motions begin at the upper ex- 
tremity of the column, near the cold air, and 
gradually extend downwards. This produces the 
characteristic inverted funnel-shaped mass of 
dark cloud by which the approach of a tornado 
is generally heralded. 

The path of the tornado, like that of the 
cyclone, is generally eastward. 

■Weather Maps. — The actual condition of the weather 
over the United States, on any day, is represented in 
weather maps published by the bureau. Two such maps 
are shown on page 152. The upper map shows the meteor- 
ological conditions prevailing on a certain day in April. 
On that day an area of low barometer existed in Colorado, 
Nebraska, and Kansas, within which the barometer was 
below 29.5 inches, as shown by the isobar, or line of mean 
barometric pressure, of 29.5. The country around this 
area had a gradually increasing barometric pressure, as 
indicated by the successive isobars 29.6, 29.7, 29.8, 29.9, 
etc. At the same time a storm was moving toward the 
north-east, as shown by the line of crosses. The rate of 
progress of the storm being known, the bureau issued the 
following 

Indications. 

For New England, fair weather followed by light rains 
to-morrow, north to east winds, slight rise in temperature. 

For the Middle Atlantic States, increasing cloudiness and 
rain, winds shifting to east and south, slightly warmer 
weather, lower barometer. 

For the South Atlantic States, local rains, warmer, partly 
cloudy weather, south-east to south-west winds, lower ba- 
rometer. 

For the East Gulf States, threatening weather and rain, 
followed by clearing weather, southerly to westerly winds, 
slight rise in temperature, followed in west portion by a 
slight fall in temperature. 

For the West Gulf States, local rains, followed by clear- 
ing weather, winds shifting to west and north, nearly sta- 
tionary, followed by lower temperature, and rising barom- 
eter to-morrow. 

For Tennessee and the Ohio Valley, cloudy weather and 
rain, southerly to westerly winds, rising temperature, fall- 
ing barometer and severe local storms, followed to-mor- 
row in west portion by cooler weather and higher barom- 
eter. 

For the Lower Lake Region, threatening weather and 
rain, east to south winds, lower barometer and rising 
temperature. 

For the Upper Lake Region, threatening weather, with 
rain or snow, north-easterly winds becoming variable, fall- 
ing followed by rising barometer, slight rise, followed by 
falling temperature. 



VEGETABLE AND ANIMAL LIFE. 



155 



For the Upper Mississippi Valley, threatening weather 
and rain, severe local storms, winds shifting to west and 
north, followed by higher barometer and colder weather. 

For the Missouri Valley, rain or snow, generally colder, 
cloudy followed by partly cloudy weather, dangerous local 
storms in southern portion, winds shifting to north and 
west, with colder weather and higher barometer. 

Light rains are indicated to-morrow for New England, 
and the Middle Atlantic States with warmer weather. 
Clearing and fair weather is indicated for the West Gulf 
States and thence northward over the Upper Mississippi, 
Missouri Valleys, and Lake Region. 

The Ohio Eiver, Cumberland, Tennessee, and the Mis- 
sissippi at St. Louis, Cairo, Vicksburg, and New Orleans, 
will continue slowly falling. 

Cautionary signals continue at Milwaukee, Chicago, 
Grand Haven, Detroit, Toledo, Sandusky, Cleveland, Erie, 
and Buffalo. 

The lower map shows the actual conditions of the weather 
on the following day. The area of low barometer, or storm- 
centre, has moved eastward and the storm is now central 
over Western Pennsylvania and the adjoining States. The 
actual condition of the weather, showing the correctness 
of the predictions, will be seen from an inspection of the 
following synopsis issued by the bureau : 

Synopsis for the Past Twenty-four Hours. 

The severe storm which was central in the Lower Mis- 
souri Valley yesterday morning moved directly east, 
causing dangerous gales on the Lakes and general rains 
in the Southern States, the Middle States, and the Ohio 
Valley. Snow and rain continue in the Lake Region this 
morning. Threatening weather is reported from New 
England, and colder, fair weather from the north-west and 
south-west. The temperature has fallen about 10° in the 
Mississippi, Ohio, and Missouri Valleys and Upper Lake 
Region, with north to west winds ; and it has risen slightly 
in the districts on the Atlantic coast, with north-easterly 
winds in New England and on the Middle Atlantic coast, 
and south-westerly winds in the South Atlantic States. 
The barometer is unusually low near Pittsburg, and it is 
highest in Nebraska. A light norther prevails on the 
Texas coast. 



oXKo 



CHAPTER III. 
Vegetable and Animal Life. 

402. Vegetation.— The distribution of vegeta- 
tion throughout the United States is in accord- 
ance with the distribution of the rainfall. Four 
characteristic plant regions are found : the Forest, 
the Prairie, the Steppe, and the Pacific Region. 

403. The Forest Region.— The chief requisite 
of forest growth — an abundant rainfall, well dis- 
tributed throughout the year or during the time 
the trees are growing — is found especially in the 
country east of the Mississippi, where luxuriant 
forests exist, unless removed by civilization. 

The pine, spruce, hemlock, fir, larch, juniper, 



and deciduous trees, such as the beech, maple, 
birch, alder, and poplar, are common in the 
North. 




Fig. 130, 



in a Pine Woods. 



Deciduous trees characterize the middle por- 
tions of the forest region. In the number and 
variety of its species, the oak is peculiarly cha- 
racteristic of the middle part of the forest region. 

In the southern portion of the forest region 
evergreen trees, such as the live-oak and the 
magnolia, are characteristic. 




Fig. 131. Raftins 



The forests have been removed, over extended 
areas, from all three parts of the forest region. 



156 



PHYSICAL GEOGRAPHY. 



The cut logs, when the river-courses are suf- 
ficiently large, are transported to different sec- 
tions of the country in huge rafts. 

404. The Prairie Region. — West of the Mis- 
sissippi Valley, to the Plateau of the Great 
Plains, the comparatively scanty rainfall pro- 
duces extensive prairies, covered with grasses 
and flowering herbs. Forests are wanting, ex- 
cept along the river-courses. 

405. The Steppe Region. — From the western 
limits of the Great Plains to the Sierra Nevada 
and Cascade ranges, lie the elevated plateaus of 
the predominant mountain-system. Here the 
rainfall is irregular and scanty, and the vege- 
tation presents the peculiarities of a true steppe. 
But few species of plants occur ; the cactus and 
wild sage are characteristic. 

406. The Pacific Region. — From the western 
limits of the steppe region to the Pacific coast, lies 
a region whose features, in some respects, resemble 
those of the forest region. In Washington and 
Oregon dense forests of fir and spruce trees occur. 
The cedar, larch, maple, oak, and chestnut are 
common. In California the periodical rainfall 
nearly excludes the forest from the valleys and 
plains ; but on the mountain-slopes, where rains 
are more frequent, well-marked forests abound. 
The pine, fir, and oak are characteristic. 

On the slopes of the coast mountains and the Sierra 
Nevada and Cascade Eauges, dense forests of pine and fir 
trees are found. In some parts of these regions the trees 
frequently attain an immense size, many of them exceeding 
300 feet in height. The largest are the celebrated " mam- 
moth trees of California," a species of pine. Some of these 
trees are 350 feet high, and have a circumference of 110 
feet at the base. In some of the fallen trees, the hollow, 
decayed trunks readily permit the passage of a man and 
horse. 

407. Animal Life. — The large animals now 
found in the United States are principally those 
which have been domesticated, such as the horse, 
cow, sheep, mule, goat, and the dog. 

In some of the sparsely-settled regions of the 
East, and over large areas in the West, a few wild 
animals are yet to be found. In parts of the 
Appalachian system, the black bear, panther, and 
deer are found. The moose is found in the north- 
ern parts of the United States. The immense 
herds of buffalo that once roved over the plains 
west of the Mississippi are nearly extinct. The 
grizzly bear and the wolf are found on the moun- 
tains of the Pacific slope. 

In the South, the warm, sluggish waters of the 



lower courses of the rivers and swamps, harbor 
numerous alligators. 

A number of species of serpents occur, but 
only two, the rattlesnake and the copperhead, 
are venomous. 

The manatee, or sea-cow, a curious herbivorous 
animal with paddle-like legs, found in the shal- 
low waters of the coast of Florida, sometimes 
attains a length of ten feet. 

Some species of the manatee in the North Pacific, off 
Alaska, reach thirty feet in length. 



CHAPTER IV. 

Agricultural and Mineral Produc- 
tions. 

408. Agricultural Productions* — The princi- 
pal agricultural productions of the United States 
are wheat, corn, rye, oats, barley, buckwheat, hay, 
hops, potatoes, flax, tobacco, rice, cotton, and 
sugar. 

409. The Cereals, ivheat, com, rye, oats, barley, 
and buckwheat, are grown principally north of the 
86° of north latitude. According to the census 
of 1890, the States giving the largest yield of 
corn were Iowa, Illinois, Kansas, and Nebraska, 
while those yielding the most wheat were Min- 
nesota, California, Illinois, and Indiana. 

The yield of corn is greater than that of any other 
cereal; the corn-crop of the year 1893, in the United 




Fig, 132. Corn-Field, 

States, amounted to 1,619,496,131 bushels. The wheat- 
crop of 1893 amounted to 395,131,725 bushels. 

* For Synopsis of Census Reports, see Table, page 175. 



AGRICULTURAL AND MINERAL PRODUCTIONS. 



157 



410. Tobacco and Flax are raised in large 
quantities in various sections of the country. 

The principal tobacco-producing States are 
Kentucky, Virginia, North Carolina, Tennessee, 
Pennsylvania, and Wisconsin. 

The entire yield of tobacco in 1893 was 483,023,963 
pounds. 




Fig. 133. Tobacco Field, 

The principal flax-producing States are Minne- 
sota, Iowa, South Dakota, and Nebraska. 

The total value of flax-products in 1893 was $11,137,896. 

411. Cotton, Kice, and Sugar are cultivated 
mainly south of the 36° north latitude. 

The principal cotton-producing States are 
Texas, Mississippi, Alabama, South Carolina, 
Georgia, Arkansas, and Louisiana. 




Fig. 134. Cotton. 

The cotton-crop of the year 1894 in the United States 
18 



amounted to 7,527,211 bales, of an average net weight of 
440 pounds per bale. 

412. The principal rice-producing States are 
South Carolina, Louisiana, Georgia, and North 
Carolina. The rice-fields are confined to low, flat, 
marshy tracts, near the coast or river bottoms. 




Fig. 135, Kice 



The principal sugar-producing State is Louis- 
iana, the plantations being confined mainly to the 
rich lands in the neighborhood of the Mississippi 
Delta. Sugar is also grown in South Carolina, 
Tennessee, and Texas. 




Fig, 136, Sngar-Cane Field, 

The total production of cane-sugar in 1893 amounted to 
450,000,000 pounds. 
Beet-sugar is produced in several of the States, princi- 



158 



PHYSICAL GEOGRAPHY. 



pally in California. The entire production in 1893 was 
27,083,322 pounds. 

Maple-sugar is produced iu Vermont, New York, Ohio, 
New Hampshire, Michigan, and Indiana. The total pro- 
duction in 1893 amounted to 3,220,000 pounds. 

413. Mineral Productions. — The United States 
are particularly noted for the richness and variety 
of their mineral dejiosits. Nearly all the import- 
ant metals are found in various portions of the 
country, some of the deposits extending over 
areas of enormous extent. 

414. Precious Metals. — Gold, silver, and plati- 
num occur. The deposits of gold and silver are 
large. 

Gold. — The principal deposits of gold occur 
in the mountainous districts in the eastern and 
western portions of the country. The Californian 
region, which embraces the entire western coast 
and much of the country as far east as the Great 
Plains, is the richest. The deposits are especially 
valuable in the basins of the Sacramento and San 
Joaquin Rivers. Gold is found either in quartz 
veins or in alluvial deposits. 

Silver is found either in the gold-fields already 
mentioned, or in deposits of galena, one of the 
most valuable ores of lead. It also occurs pure 
or native in the copper regions of Lakes Superior 
and Michigan. 

Platinum has been found in small quantities 
in both the eastern and western portions of the 
country. 

415. Ordinary Metals. — Iron, copper, zinc, and 
lead occur in various portions of the eastern, cen- 
tral, and western sections of the country. 

Iron, which intrinsically is the most valuable 
of all the metals, is, perhaps, the most widely 
distributed. Valuable deposits of various iron 
ores, mainly oxides and carbonates, occur in 
many parts of the country. The deposits are ex- 
ceedingly rich in Northern Michigan and Wis- 
consin ; in the neighborhood of the Adirondacks 
in New York; in Pennsylvania; in Missouri, 
where the deposits at one time actually formed 
two mountains of iron ; in the district of Lake 
Superior; in Alabama, and elsewhere. The de- 
posits in Pennsylvania are the most valuable, from 
their vicinity to beds of coal and limestone, which 
are necessary for the reduction of the ore. 

Copper occurs in large quantities in the east- 
ern, western, and central sections of the country. 
The ores are principally sulphides or oxides, or 
the native or metallic copper. The most valu- 
able deposits are found in the neighborhood of 



Keweenaw Point, Lake Superior, where large 
beds of the native material occur. 

Zinc. — The most valuable deposits are found in 
Missouri, Wisconsin, and Kansas. It also occurs 
in the Atlantic States, from Maine to Virginia. 

Lead. — Valuable deposits are found in the East, 
from Maine to North Carolina. The largest and 
richest districts, however, are in the interior, in 
Colorado and Utah, where it occurs with silver, 
and in the Mississippi Valley ; in Wisconsin, 
Iowa, Illinois, and Missouri. 

416. Among other valuable metals, tin, mer- 
cury, chromium, nickel, cobalt, antimony, bis- 
muth, manganese, are found in small quantities. 

Tin occurs in limited quantities both in the East 
and in the West. So far as is known, the deposits 
are richest in the Black Hills in Dakota. 

Mercury is found either pure or in combina- 
tion. The principal ore is the sulphide of mer- 
cury or cinnabar. The deposits in California are 
the most important. 

Chromium is found in moderately large quan- 
tities in various portions of the Atlantic States, 
as far south as Virginia. 

Nickel, cobalt, antimony, bismuth, and man- 
ganese are found in limited quantities. 

417. Coal, — The coal-fields of the United States 
are the richest in the world. Immense deposits 
occur in the eastern, central, and western sections 
of the country. So far as is known, the eastern 




Pig. 137. Ooal-Mine. 

coal-field, which covers portions of Pennsylvania, 
Ohio, Virginia, Kentucky, Tennessee, and Ala- 
bama, is the most extensive. 



AGRICULTURAL AND MINERAL PRODUCTIONS. 



159 



Other coal-fields occur in Illinois and Missouri, 
in Texas, Michigan, Rhode Island, and New 
Brunswick and Nova Scotia, 

The area of the coal-fields of Western Europe is estimated 
by Dana at about 20,000 square miles, while the total area 
of those of the United States probably exceeds 125,000 
square miles. In the United States, Pennsylvania possesses 
the most extensive and the richest deposits, the total area 
of the deposits in this State being nearly 20,000 square 
miles, or equal to those of Western Europe. The richness 
of the American coal-fields cannot fail to exert an import- 
ant influence on the future development of the country. 

418. Peat-Bogs of Massachusetts. — Peat con- 
sists of a black, carbonaceous deposit which ac- 
cumulates in badly-drained regions of humid 
climates. The surfaces of the peat-marshes are 
often covered with a thin crust, formed by the 
interlacing roots of vegetable growths. Below 
this crust is a treacherous, oozy quagmire. 

When peat is dried it is suitable for fuel. 
Dana estimates that Massachusetts contains fifteen 
billion cubic feet of peat. Large deposits occur in 
the Great Dismal Swamp, in North Carolina and 
Virginia. 

419. Petroleum, or Coal Oil, is found in various 




Pig. 138. Oil Well and Tank. 

sections. The most valuable deposits occur in a 
region embracing Western Pennsylvania, Vir- 
ginia, Ohio, and Michigan. Petroleum is found 
also in the West. 



The oil is obtained by boring. The wells so 
produced are similar to artesian wells, excej)t in 
the material discharged. In many instances the 
oil issues in powerful streams, which continue to 
flow for considerable periods. The crude oil is 
generally stored in huge tanks, from which it is 
transferred to barrels or iron tanks for trans- 
portation. Much is also distributed for great dis- 
tances through lines of pipes called pipe-lines. 
For most commercial uses it is necessary to re- 
fine or purify the oil. 

420. Natural Gas. — Accumulations of natural 
or rock-gas occur in nearly all portions of the 
United States, but such deposits are especially 
rich in the regions where coal oil is found. 
Western Pennsylvania, and the adjoining States, 
yield great quantities of such gas. 

The gas is obtained by borings similar to those 
made for artesian wells or coal-oil wells. From 
the gas wells thus formed the gas issues forth with 
great velocity. When lighted it burns with a 
flame similar to that of ordinary illuminating 
gas. Like ordinary gas it burns with a pale 
bluish flame when mixed with air, and affords 
an excellent source of artificial heat. 

Natural gas has been known for many years past, but it 
is only recently that its great extent and quantity have 
been ascertained. In many districts — notably in the city 
of Pittsburgh and vicinity — natural gas has practically 
superseded illuminating gas as a source of light, and has 
almost entirely replaced ordinary coal as a source of heat. 
The value of such a natural product in any manufacturing 
centre can scarcely be overestimated, and its successful in- 
troduction in any locality has in all cases been attended 
with a marked growth in the extent and variety of its 
manufactures. Although such deposits must in perhaps a 
comparatively short time become exhausted, as yet they 
show but little signs of failure. 

The gas escapes from the well under great pressure. 
Before its delivery to consumers, through pipes like ordi- 
nary gas-pipes, the pressure is reduced by suitable contri- 
vances ; so that its consumption is not attended with any 
greater risk than that attending ordinary illuminating gas. 

421. Salt. — Beds of rock-salt occur in Louisi- 
ana, Virginia, and in various parts of the West. 
Large quantities are obtained by evaporatiug the 
waters of saline or brine springs. These are of 
common occurrence. The most valuable are 
found in New York, in the neighborhood of 
Salina and Syracuse ; in Virginia, Michigan, Ken- 
tucky, and in the Far West. 

422. Building Stones. — Large deposits of valu- 
able building stones are found in all parts of the 
country. Among the most common are various 
kinds of sandstone, marble, granite, slate, mag- 
nesian limestone, serpentine, gneiss, and mica 



160 



PHYSICAL GEOGRAPHY. 



schist. Valuable deposits of clay occur, from 
which excellent bricks are made. 



CHAPTER V. 
Alaska. 

423. Extent of Territory.— The Territory of 
Alaska, now a part of the domain of the United 
States, embraces the north-western part of the 
North American Continent, and extends south 
from the shores of the Arctic Ocean to about 54° 
of N. lat. The main part of the Territory lies west 
of the 141° E. long, from Greenwich. South of 
Mt. St. Elias, however, it embraces a narrow 
strip extending south-eastwardly along the coast 
of British Columbia. 

The Territory of Alaska embraces an area of 
about 530,000 miles, or, approximately, about 
one-sixth of the whole area of the remainder of 
the domain of the United States. This country 
was purchased from Russia by the United States 
in 1867, at a cost of $7,200,000. 

Indentations of the Coast. — The coast-line of 
Alaska is exceedingly irregular, its entire length 
amounting to as much as 8000 miles. The shores 
of the Arctic are the least indented. The western 
and southern coasts are deeply indented. 

Bering Sea and Straits separate Alaska from 
Asia. The Pacific Ocean enters the wide curve 
of the southern coast as the Gulf of Alaska. 
Smaller indentations on the western coasts are 
found in Norton Sound, Kuskovitch Bay, Bristol 
Bay, and in the numerous bays and inlets on the 
southern coasts, in which true fiords occur. 

424. Islands. — Numerous islands lie off the 
western and southern coasts. The principal of 
these are St. Lawrence Island and Nunivak, on 
the western coast ; the Aleutian Islands, which ex- 
tend in a curve from the Alaskan Peninsula 
nearly to Kamtchatka; Afognak and Kadiak 
islands, off the southern shores of the peninsula; 
and BaranofF, Chichagof and Prince of Wales 
islands off the south-eastern shores. 

425. Surface Structure. — The northern portions 
of Alaska are low and flat, and the plains, drained 
by a few small, sluggish streams, are, for the most 
part, frozen moor-lands, similar to the tundras of 
Northern Siberia. They form a dreary, desolate 
country, for the greater part unexplored, covered 



during the brief summer by a comparatively 
dense growth of grasses. 

The rest of Alaska is generally mountain- 
ous, being traversed by prolongations of the 
Pacific Mountain -System. The highest eleva- 
tions are those of the south-eastern coast, Mt. St. 
Elias being 19,500 feet above the level of the 
sea. Mts. Crillon and Fairweather are scarcely 
inferior in height. These mountains contain nu- 
merous glaciers which descend nearly to the level 
of the sea. The chain of the Aleutian Islands 
is mountainous, and, like the mountains of the 
south-western coast, contains many volcanic 
peaks. 

426. Drainage System. — The principal river 
of Alaska is the Yukon, which, so far as known, 
has a length of at least 2000 miles. It is one of 
the largest rivers in North America, so far as 
the volume of its discharge is concerned, which 
appears to be as great as that of the Missis- 
sippi. In some portions of. its lower course it 
is, in places, 20 miles wide. An extensive delta 
formation occurs at the mouth of the river. The 
Lewis and the White, its principal tributaries, are 
situated near the head-waters of the Yukon, in 
the Dominion of Canada. 

The Kuskovim is the only other important 
river. Unlike the delta-mouth of the Yukon, 
the Kuskovim discharges its waters into Bering 
Sea through a wide estuary. The spring tides 
sometimes rise in this estuary to the height of over 
50 feet. 

The glaciers of the south-eastern coast feed a 
number of lakes, so near together as to permit 
the establishment of portage-routes of travel. 

427. Climate. — The climate of Alaska is, gen- 
erally, cold and wet, although the influence of 
the Japan Current, and the westerly winds and 
rain, render the mean annual temperature much 
warmer than corresponding latitudes in the inte- 
rior, or even on the eastern coasts of the North 
American Continent. Fogs and rains are fre- 
quent. The annual rainfall at Sitka, on Baranoff 
Island, is about 85 inches. 

428. Vegetation. — Dense grasses cover por- 
tions of the tundras, river valleys, and hillsides 
during the brief summer. The wet climate, how- 
ever, renders the curing of hay a difficult matter, 
and, consequently, the rearing of cattle is attended 
with difficulty. 

Portions of the lower mountainous slopes and 
river valleys are covered with forests of yellow 
cedar and spruce. In the greater part of the 



Territory no timber grows at an altitude greater 
than 1000 feet above the sea. Turnips, potatoes, 
and radishes have been cultivated in southern 
portions of the Territory with fair success. 

429. Animal Life. — The rivers are visited dur- 
ing the breeding season by myriads of salmon. 
This fish forms the principal food of the inhabit- 
ants, who, at the beginning of the season, desert 
the interior for the banks of the rivers. Halibut, 
herring, codfish, and mackerel, are caught off the 
coasts of the Territory . 

The fur seal, the walrus, and the sea-rotter are 
caught in great numbers for their valuable fur. 
The whale is found in the Arctic waters of the 
northern coast. The polar bear, the brown bear, 
the mink, the black or silver fox, the moose, and 



the reindeer are also found in the Territory. 
Dense swarms of bloodthirsty mosquitoes and 
black flies occur in nearly all parts of the 
country. 

430. Minerals. — Beds of coal of an inferior 
quality have been discovered in various parts 
of the country. Deposits of silver, gold, cop- 
per, lead, and cinnabar also occur. 

431. Inhabitants. — The inhabitants of Alaska 
consist principally of the Esquimaux or Innuit, 
the Indians, and the Aleuts, or the inhabitants 
of the Aleutian Islands, the Creoles or Russian 
half-breeds, and the inhabitants of the remaining 
archipelagoes, together with a few whites. 

Sitka, on Baranoff Island, is the principal set- 
tlement. 



SYLLABUS. 



«* 



The area of the United States, exclusive of Alaska, is 
about 3,000,000 square miles. 

The coast line is comparatively simple and unbroken. 
The principal indentations on the east are Long Island 
Sound, Delaware and Chesapeake Bays, and Albemarle and 
Pamlico Sounds ; on the west, the Gulf of Georgia and the 
Bay of San Francisco. 

The slope of the Atlantic shores is gradual; that of the 
Pacific shores is abrupt. 

On the Atlantic coast, the islands north of Cape Cod are 
for the most part rocky ; those south of Cape Cod are gen- 
erally low and sandy. 

Mangrove islands are formed by sediment collecting 
around the closely intertwined roots of mangrove trees. 
These islands occur in the shallow waters off the coast of 
Florida. 

Nearly all of Florida, south of the Everglades, and 
probably as far north on the eastern coast as St. Augus- 
tine, consists of a peculiar variety of coral formation. 

The Pacific system is the predominant mountain-system ; 
the Appalachian system is the secondary system. 

The Pacific system consists of the Eocky Mountains, the 
Sierra Nevada, the Cascade, and the Coast Mountains. 

The highest peaks are found in the Cascade Mountains. 

Portions of the Pacific Mountain ranges contain extinct 
volcanoes. 

The Appalachian system, or the system of the Allegha- 
nies, includes the White Mountains, the Green Mountains, 
the Adirondacks, the Catskills, the Blue Eidge, and the 
Cumberland Mountains. 

There aTe two great low plains in the United States : the 
Atlantic Coast Plain and the Plain of the Mississippi 
Valley. 

The principal rivers draining into the Atlantic Ocean 
are the Penobscot, Merrimac, Connecticut, Hudson, Dela- 
ware, Susquehanna, Eoanoke, Cape Fear, Santee, Savan- 
nah, Altamaha, and St. John's. 



The principal rivers draining into the Mexican Gulf are 
the Appalachicola, Alabama, Mississippi, Sabine, Trinity, 
Brazos, Colorado, and the Eio Grande. 

The principal rivers draining into the Pacific Ocean are 
the Columbia, Sacramento, San Joaquin, and the Colorado. 

The Great Basin, between the Wahsatch and the Sierra 
Nevada Mountains, has an inland drainage. 

Soda Valley, in Southern California, and Death Valley, 
in Eastern California, are below the level of the sea. 

The Great Lakes, Superior, Michigan, Huron, Erie, and 
Ontario, form the largest system of fresh-water lakes in 
the world. 

The United States extends from the isotherm of 40° Fahr. 
to 77° Fahr., and therefore lies in the physical north tem- 
perate and the torrid zones. 

A marked contrast exists between the temperature of 
the eastern and the western coasts of the northern half 
of the country. The eastern coasts are colder than the 
western. 

The greater warmth of the western coasts is caused by 
warm ocean currents, westerly winds, and heavy rainfalls. 

The Atlantic seaboard is colder than corresponding lati- 
tudes on the western shores of Europe or on the western 
shores of the United States. 

From observations dating back to the year 1738 it ap- 
pears that from that time the climate of the United States 
has undergone no decided change. 

The United States lies in the zone of the variable winds ; 
westerly winds predominate. 

The heaviest annual rainfall is 65 inches. It occurs near 
the borders of the Gulf States and along the Pacific sea- 
board in Washington and Oregon. The smallest annual 
rainfall is found in the Great Basin , it varies from 5 to 10 
inches. East of the 100th meridian from Greenwich the 
average fall is 40 inches. 

On the Atlantic coast rain is especially abundant during 
spring ; on most of the Pacific coast, during winter. 



162 



PHYSICAL GEOGRAPHY. 



The Weather Bureau was established for the observation 
of the meteorological conditions of the country. 

There are four characteristic plant regions in the 
United States: the Forest, the Prairie, the Steppe, and 
the Pacific. 

The forest region lies mainly east of the Mississippi ; the 
characteristic trees are the pine, spruce, hemlock, fir, juni- 
per, beech, maple, birch, alder, oak, and poplar. 

The principal large animals of the United States are 
those which have been domesticated, as the horse, ox, 
cow, sheep, mule, goat, and dog. 

Among wild animals are the black bear, panther, deer, 
grizzly bear, wolf, and manatee or sea-cow. 

The principal agricultural productions are wheat, corn, 
rye, oats, barley, buckwheat, hay, hops, flax, tobacco, rice, 
cotton, and sugar. 

The principal metals are gold, silver, platinum, iron, 
copper, zinc, lead, tin, mercury, chromium, nickel, cobalt, 
antimony, bismuth, and manganese. 

Deposits of coal, rock-salt, marble, coal oil, and natural 
gas are found, and many varieties of durable building- 
stone. 

Extensive peat-bogs occur in Massachusetts and Virginia. 

The Territory of Alaska has an area of about 530,000 
square miles and is nearly one-sixth that of the area of the 
rest of the domain of the United States. 

The coast line of Alaska is very irregular, and has a 
length of at least 8000 miles. 

Bering Sea on the west, and the Gulf of Alaska on the 
south, are the principal indentations of the coast. Norton 
Sound and Kuskovitch and Bristol Bays are among the 
most important of the smaller indentations. 

The principal islands are St. Lawrence Island, Nunivak, 



the Aleutian Islands, Afoguak, Kadiak, Baranoff, Chicha- 
gof, and Prince of Wales. 

The northern portions of Alaska are low and flat, and 
are covered by tundras or frozen moor-lands. The rest of 
the country is generally mountainous, and is traversed by 
prolongations of the Pacific Mountain system of North 
America. Mts. St. Elias, Fairweather, and Crillon are 
the principal peaks. 

The principal river of Alaska is the Yukon, which is 
some 2000 miles long, and is one of the largest rivers of 
the North American Continent. The Kuskovim is the 
only other important river. The Yukon has a delta 
mouth — the Kuskovim, an estuary. 

The climate of Alaska is cold and wet, though, under 
the combined influences of the Japan current, the rains, 
and the warm south-westerly winds, the climate is less 
severe than at corresponding latitudes in the interior, or 
on the Atlantic coast. 

Dense growths of grasses abound during the brief sum- 
mer. Forests of yellow cedar and spruce occur. 

The chief animals are the polar and brown bears, the 
mink, black or silver fox, the moose, and the reindeer. 
The whale is found in the waters off the northern shores, 
and the walrus, the seal, and the sea-otter are sources 
of wealth by reason of their valuable furs. Salmon, hali- 
but, cod, and herring, are the principal food-fish. 

Deposits of coal, silver, gold, lead, and cinnabar occur in 
different parts of the country. 

The inhabitants consist of various elements, the princi- 
pal of which are the Esquimaux, the Indians, the Aleuts, 
the Creoles, and the people of the archipelagoes of the 
southern and south-eastern coast. 

Sitka, on Baranoff Island, is the principal settlement. 



REVIEW QUESTIONS. 



oXKo 



State the geographical position of the United States. 

Describe the peculiarities of its coast lines. 

Name the principal indentations of the eastern coast. 
Of the western coast. 

In what respect do the islands which lie north of Cape 
Cod differ from those which lie south of it? 

What is the origin of the islands off the southern coast 
of Florida? 

Describe the Pacific Mountain system. Locate the Great 
Plains. The Great Basin. 

Describe the Appalachian Mountain system. 

Name the great low plains of the United States. 

Name the important rivers which drain directly into 
the Atlantic; name those which drain into the Atlantic 
through the Gulf of Mexico ; name those which drain into 
the Pacific. 

What system of inland drainage is found in the United 
States? 

Describe the lake-systems of the United States. 

In what mathematical zone is the United States situated ? 
In what physical zones? 

Between what isothermal lines does the United States 
extend? 

Describe the general direction of the isotherm of 40° 
Fahr. Of 55° Fahr. Of 60° Fahr. 

What difference exists between the climate of the eastern 
and western coasts ? What are the causes of this difference ? 



Has the climate of the United States undergone any de- 
cided change during the last hundred years ? 

In what wind zone does the United States lie? 

In what parts of the country does the heaviest annual 
rainfall occur? The smallest annual rainfall? 

What is the rainfall of the upper Mississippi Valley? 
Of the lower Mississippi ? 

At what season of the year do the heaviest rains occur 
on the Atlantic coast ? On the Pacific coast ? 

For what was the Weather Bureau established ? 

What are tornadoes ? 

Under what four characteristic plant regions may the 
vegetation of the United States be arranged? 

Describe the location of each of these regions. 

Name the principal forest trees of the United States. 

Name the principal domesticated and wild animals ot 
the United States. 

Enumerate the principal agricultural productions. 

Name the principal corn-producing States. The prin- 
cipal wheat-producing States. 

Name the principal cotton-producing States. The prin- 
cipal rice-producing States. The principal sugar-producing 
States. 

What valuable metals are found in the United States? 

What other valuable mineral substances occur? 

What are the limits of the Territory of Alaska? State 
its boundaries. What is its area ? 



GENERAL SYLLABUS. 



163 



What sum was paid for Alaska by the United States 
Government? 

Name the principal indentations of the coast of Alaska. 
What is the extent of its coast line ? 

Name the principal islands of the western coast. Of the 
southern coast. 

Describe the surface structure of Alaska. To what gen- 
eral system of mountains do its elevations belong? Name 
some of the principal peaks. Are any of them volcanic ? 

Describe the river-system of the Yukon. Where is the 
Kuskovim Eiver? Which of these rivers has a delta 
mouth ? Which has an estuary ? 



What is the general climate of Alaska? How does the 
climate compare with that of corresponding latitudes in 
the interior of the country or on the Atlantic coast ? Why 
is this ? 

Describe the vegetation of Alaska. What are the prin- 
cipal trees? 

Name the principal food-fish of Alaska. Name the prin- 
cipal fur-bearing animals. What other large animals are 
found in the country ? 

Which is the principal settlement? Name some of the 
different people who inhabit Alaska. 



MAP QUESTIONS. 



Describe from the Physical Map of the United States 
the surface structure of the country, giving the relative 
position of the High Lands and Low Lands. 

Describe the Pacific Mountain System. 

Describe the Appalachian Mountain System. 

Locate the following : the Black Hills ; the Wahsatch 
Mountains ; the Sierra Madre ; San Louis Park ; Pike's 
Peak ; Long's Peak ; Fremont's Peak. 

Describe the drainage of the Great Lakes. 

Name the principal rivers which empty into the Atlantic. 
Into the Gulf of Mexico. Into the Pacific. 

Name the principal tributaries of the Mississippi. 

Where are the Santa Barbara Islands? The Bahama 
Islands? Vancouver's Island? 



Trace on the map the isothermal line of 45°. 

What is the cause of the southward deflection of 
the isothermal lines in the western part of the United 
States ? 

Prove from the isotherms that the climate of the 
northern half of the Atlantic coast is colder than the 
southern half. 

In what portions of the United States is the lowest mean 
annual temperature found ? The highest ? 

Name the swamps and sounds of the Atlantic sea- 
board whose formation is to be traced to fluvio-marine 
deposits. 

What swamp is due to coral formations ? 



»§=&§= 



GENERAL SYLLABUS. 



o!«o» 



Physical Geography treats of the distribution of the land, 
water, air, plants, animals, and minerals of the earth. 

The earth moves through empty space around the sun. 
It is kept in motion in its orbit by its inertia and the 
attraction of the sun. 

The rotundity of the earth is proved — 1. By the ap- 
pearance of approaching or receding objects ; 2. By the cir- 
cular shape of the horizon ; 3. By the shape of the earth's 
shadow ; 4. By the great circle of illumination ; 5. By 
actual measurement. 

Exact geographical position is determined by reference 
to certain imaginary lines called parallels and meridians. 

Representations of the whole or of parts of the earth's 
surface are made by means of maps. 

Maps are drawn on different projections : the Equa- 
torial, the Polar, and Mercator's projection are in the most 
general use. 

The length of daylight in either hemisphere depends on 
the extent to which that hemisphere is inclined towards 
the sun ; the longest day in the northern hemisphere occur- 
ring June 21st, when the sun is vertical over the Tropic of 
Cancer. 

The change of seasons is occasioned by the revolution 
of the earth, together with the inclination of the earth's 
axis at an angle of 66° 33' to the plane of its orbit, 



and the constant parallelism of the axis with any former 
position. 

The Torrid Zone is the hottest part of the earth, because, 
at one time or another throughout the year, every part of 
its surface receives the vertical rays of the sun. 

The following different opinions are held concerning the 
condition of the interior of the earth : 

(1.) That the earth has a solid centre and crust, with a 
heated layer between. 

(2.) That the crust only is solid, and the remainder suf- 
ficiently heated to be in a fused or pasty condition. 

(3.) That the earth is solid throughout, but highly heated 
in the interior. 

The proofs of the present highly-heated condition of 
the interior of the earth are as follows: 

1. In all parts of the earth, the deeper we penetrate the 
crust, the higher the temperature becomes ; that is to say, 
the entire interior is heated. 

2. The presence of volcanoes, which, in all latitudes, 
eject melted rock from the inside of the earth ; that is to 
say, the entire interior is filled with matter sufficiently hot 
to melt rock at ordinary pressures. 

3. The occurrence of earthquake shocks in all parts of 
the earth. 



164 



PHYSICAL GEOGRAPHY. 



The original fluidity of the earth is rendered probable by 
the following circumstances: 

(1.) By the spherical shape of the earth. 

(2.) The crystalline rocks, or those formed in the presence 
of great heat, underlying all others. 

(3.) The warmer climate of the earth during the geolog- 
ical past. 

Volcanoes eject from the interior of the earth — 1. 
Melted rock or lava; 2. Showers of ashes or cinders; 3. 
Vapors or gases. 

These materials are brought up from great depths into 
the volcanic mountain by the force caused by a contract- 
ing globe. They may escape from the crater — 1. By the 
pressure of highly-heated vapors; 2. By the pressure 
exerted by a column of liquid lava. 

All volcanoes are found near the coasts of the continents, 
or on islands. 

The movements of the earth's crust produced by earth- 
quake shocks are — 1. A wave-like motion around the 
centre of disturbance ; 2. An upward motion ; 3. A rotary 
motion. 

The following facts have been discovered as regards 
earthquakes : 

(1.) Their place of origin is not very deep seated. 

(2.) The area of disturbance increases with the energy 
of the shock and the depth of its origin. 

(3.) The shape of its origin is that of a line and not 
that of a point. 

(4.) The shape of the area of disturbance varies with 
the elasticity of the materials through which the shock 
moves. 

(5.) The earthquake motion travels as spherical waves, 
which move outward in all directions from their point 
of origin. 

The most violent earthquake shocks continue but for a 
short time. 

Earthquakes are generally caused by the strain produced 
by the contraction of the crust. 

Earthquake shocks are of more frequent occurrence — 1. 
In winter than in summer ; 2. At night than during the 
day ; 3. During the new and full moon, than during any 
other phase. 

Earthquake shocks may occur in any part of the world, 
but are of most frequent occurrence in the neighborhood 
of volcanoes. 

Eocks may be divided, according to their origin, into three 
classes: 1. Igneous; 2. Aqueous; 3. Metamorphic. 

They may be divided according to their condition, into — 
1. Stratified ; 2. Unstfatified. 

Unstratified rocks are either igneous or metamorphic. 

Eocks which contain organic remains are said to be 
fossiliferous ; if destitute of these remains, non-fossil- 
iferous. 

Stratified rocks are sometimes called fragmental. Un- 
stratified rocks are sometimes called fragmental. Aqueous 
rocks are sometimes called sedimentary. 

During the geological past extensive changes occurred in 
the land and water surface of the earth, and in the plants 
and animals inhabiting it. 

The changes now occurring in the earth's crust are 
caused — 1. By the winds; 2. By the moisture of the 
atmosphere; 3. By the action of running water; 4. By 
the agency of man ; 5. By the action of the heated in- 
terior. 

Of the 197,000,000 square miles of the earth's surface, 
144,000,000 square miles are covered by water, and 
53,000,000 by land. The proportion between the land 



and water is very nearly as the square of three is to the 
square of five. 

The continents extend farther to the north than to the 
south ; they are crowded together near the north pole. 
Their southern projections are separated from each other 
by extensive oceans. 

Nearly all the land masses are collected in one hemi- 
sphere, and a large part of the water in another. 

There are two great systems of trends or lines of direc- 
tion, along which the shores of the continents, the moun- 
tain-ranges, the oceanic basins, and the island chains 
extend. 

The main prolongation of the eastern continent is in the 
direction of the north-eastern trend ; the western, in that 
of the north-western trend. 

The coast lines of the northern continents are very irreg- 
ular, the shores being deeply indented with gulfs and bays, 
while those of the southern continents are comparatively 
simple and unbroken. 

Of the 53,000,000 square miles of the land, 3,000,000, or 
about one-seventeenth, is composed of islands. 

Islands are either continental or oceanic. 

Continental islands are detached portions of the neigh- 
boring continents. 

Oceanic islands are the summits of submarine mountain- 
chains. They are either high or low : the high oceanic 
islands are generally of volcanic formation ; the low islands 
are of coral formation. Mangrove islands occur off the 
coasts of Florida. 

There are four varieties of coral formations : 1. Fringing 
reefs ; 2. Barrier reefs ; 3. Encircling reefs ; 4. Atolls. 

A peculiar variety of coral reef occurs off the coasts of 
Florida. 

The subsidence of the ocean's bed is proved — 1. By the 
exclusive occurrence of volcanoes on the shores of the con- 
tinents or on islands; 2. By the occurrence of atolls or 
coral islands; 3. By the general direction of the continen- 
tal island chains. 

The earth's surface is composed of high lands and low 
lands. The dividing line is 1000 feet above the level of 
the sea. 

High lands are either mountainous or plateaus. 

Low lands are either hills or plains. 

About one-half of the laud surface of the earth is occu- 
pied by plains. 

Plains are 1. Undulating ; 2. Marine ; 3. Alluvial. 

Mountains were formed by the contraction of the earth's 
crust, producing a lateral pressure on extended, thick de- 
posits of sedimentary rocks. Slaty cleavage was caused 
by this lateral pressure. 

The following peculiarities are noticeable in the relief 
forms of the continents : 

1. The continents have, in general, high borders and a 
low interior. 

2. The highest border lies nearest the deepest ocean ; 
hence, the culminating point, or the highest point of land, 
lies out of the centre of the continent. 

3. The greatest prolongation of a continent is always 
that of its predominant mountain-system. 

4. The prevailing trends of the mountain masses are the 
same as those of the coast lines, and are, in general, either 
north-east or north-west. 

Water acquires its maximum density at about the tem- 
perature of 39.2° Fahr. 

Water requires more heat to warm it, and gives out more 
on cooling, than any other common substance. 

During the constant washings to which the continents 



GENERAL SYLLABUS. 



165 



are subjected by the rains, their surfaces are cleaused of 
the decaying animal and vegetable matters which cover 
them. 

The drainage of the land is of two kinds : subterranean 
and surface drainage. 

Surface drainage is either oceanic or inland. 

According to the size of their reservoirs, springs are 
either constant or temporary ; according to the depth of the 
reservoirs, they are either cold or hot ; according to the 
nature of the mineral substances lining their reservoirs, 
they become charged with various mineral substances; if 
their reservoirs discharge through a siphon-shaped tube, 
they are periodical ; if their reservoirs are formed of con- 
cave layers, they are called artesian springs. 

The quantity of water discharged by a river depends— 
1. On the size of its basin. 2. On the amount of its rain- 
fall. 3. On the climate of its basin, a dry, hot air dimin- 
ishing the quantity by evaporation. 4. On the nature of 
its bed or channel, whether leaky or not. 5. On the 
features of its basin, whether wooded or open. 

The material eroded by a river is deposited — 1. In the 
channel of the river. 2. On the alluvial fiats or flood- 
grounds. 3. At the mouth. 4. Along the coast near the 
mouth. 

In the upper courses of rivers erosion occurs mainly on 
the bottom of the channel ; in the lower courses, at the 
sides. 

The Atlantic and Arctic Oceans receive the waters of 
nearly all the large river systems of the world. 

Lakes connected with the system of oceanic drainage are 
generally fresh ; those connected with the inland drainage 
are generally salt. 

The bed of the ocean is less diversified than the surface 
of the land. 

The greatest depth of the ocean is probably greater than 
the greatest elevation of the land. 

The articulation of land and water assumes four dis- 
tinct forms, — inland seas, border seas, gulfs and bays, 
and fiords. 

Inland seas characterize the Atlantic ; border seas, the 
Pacific ; gulfs and bays, the Indian ; fiords, the Atlantic 
and Pacific. 

A deposit of fine calcareous mud or ooze, formed of the 
hard parts of minute animalculae, occurs over extended 
areas of the floor of the ocean. 

Tides are caused by the attraction of the sun and moon : 
spring tides by their combined attractions; neap tides, by 
their opposite attractions. 

Constant ocean currents are occasioned by the heat of the 
sun and the rotation of the earth. 

The vertical rays of the sun are warmer than the oblique 
rays — 1. Because they have a less depth of air to pass 
through. 2. Because they are spread over a smaller area. 
3. Because, striking the surface more directly, they produce 
greater heat. 

Continual summer characterizes the tropics ; summer and 
winter of nearly equal duration, the temperate zones ; and 
short, hot summers, followed by long, intensely cold win- 
ters, the frigid zones. 

The irregular distribution of heat over the earth is 
caused — 1. By the irregularities of the surface. 2. By pecu- 
liarities in the distribution of the land- and water-areas. 
3. By the influence of the winds and ocean currents. 4. 
By the nature of the surface. 

Winds are caused by the disturbance of the equilibrium 
of the atmosphere by heat. 

The general motion of the surface winds is towards an 
19 



area of greatest heat ; of the upper currents, towards an 
area of least heat. 

The general atmospheric circulation is from the equator 
to the poles, and from the poles to the equator. 

In storms, the wind has a rotary motion around an area 
of low barometer, which, at the same time, progresses along 
the surface. 

In the northern hemisphere, the rotary motion is in an 
opposite direction to the hands of a clock ; in the southern 
hemisphere, in the same direction as the hands of a clock. 

Moisture may be precipitated from the air in the form of 
dew, mist, fog, cloud, rain, hail, sleet, or snow. 

In order that any form of precipitation may occur, the 
air must be reduced below the temperature of its dew- 
point. 

Glaciers are immense masses of ice and snow, which 
move with extreme slowness down the higher valleys of 
mountain-ranges. They resemble rivers in that they re- 
ceive through the drainage of their basins, the solid 
material which flows into them. 

The snow line is the distance above the sea where the 
snow remains throughout the year. The height of its 
lower level above the sea depends (1.) On the amount of 
the snowfall. (2.) On the temperature of the valley. (3.) 
On the inclination of the slope. 

The unit of electric potential is called a volt; the unit 
of current an ampere; the unit of resistance an ohm. 
Comparing the flow of electricity to a current of water in 
a pipe, the volt corresponds to the pressure causing the 
flow, the ohm to the resistance, or friction, opposing it, 
and the ampere to the quantity of flow per second. 

The principal electrical phenomena of the atmosphere are 
thunder and lightning, St. Elmo's fire, and the aurora. 

The principal optical phenomena are the rainbow, the 
mirage, halos, and coronie. 

The earth acts like a huge magnet. Its magnetism is 
probably due to the circulation around it of electrical cur- 
rents, generated by the sun's heat. 

The true basis for the distribution of vegetation is the 
distribution of the light, heat, and moisture, upon which 
its existence mainly depends. 

The variety and luxuriance of vegetation decrease as 
we pass from the equator to the poles, or from the base 
of a mountain to the summit. 

The principal food-plants of the tropical regions are rice, 
bananas, plantains, dates, cocoa-nuts, cassava, bread-fruit, 
sago, and yams. 

Coffee, tea, cocoa, pepper, cloves, nutmegs, and vanilla 
are also products of the tropics. 

The principal food-plants of the temperate zones are 
barley, rye, wheat, oats, maize or Indian corn, buckwheat, 
and the potato. 

Animals are restricted, by conditions of food and climate, 
to certain regions of the earth. 

They are dependent for their continued existence upon 
plants, the distribution of which therefore forms an excel- 
lent basis for the distribution of animals. 

With a few exceptions, animals possess but little power 
of becoming acclimated, or living in a climate differing 
greatly from that in which they were created. 

The grassy meadows and prairies in North America cause 
the fauna of the continent to be characterized by a pre- 
ponderance of plant-eating mammals. Its extensive lake- 
and river-systems harbor a great number and variety of 
waterfowl. 

South America is characterized by the predominance of 
its reptiles and insects. Birds are also numerous. 



166 



PHYSICAL GEOGRAPHY. 



Asia is the home of domesticated animals. 

Australia is the home of the marsupials. 

The luxuriant vegetation of the south of Africa sustains 
some of the largest of the mammalia, such as the elephant, 
rhinoceros, hippopotamus, and giraffe. 

The entire human family has descended from a single 
pair or species. 

The primary races of men are the Caucasian, the Mongo- 
lian, and the Negro. 

The secondary races are the Malay, the American, and 
the Australian. 

The character of the earth's mineral products has largely 
influenced the civilization of man. 

With a few exceptions, the earth's mineral products 
that are of the greatest value to man, such as the precious 
metals, the valuable metals, building materials, and 
mineral substances used generally in the arts and in the 
sciences, are so generally distributed over the earth that 
practically they are found in all the continents. 

For a substance to be suitable for building purposes it 
must possess marked strength, ability to resist a crushing 
weight placed upon it, and to resist disintegration on long 
exposure to moisture and change of temperature. 

The coast line of the United States is comparatively 
simple and unbroken. 



The predominant mountains are in the west ; the second- 
ary mountains are in the east. 

The great low plains of the United States are the Atlantic 
coast plain and the plain of the Mississippi Valley. 

The United States lies in the physical north temperate 
and the physical torrid zone. 

The climate of the northern half of the Atlantic coast 
is much colder than that of the northern half of the 
Pacific. 

. The United States lies in the zone of the variable 
winds. 

The heaviest rainfall is on the Pacific coast and near the 
borders of the Gulf States. 

There are four distinct plant regions: the forest, the 
prairie, the steppe, and the Pacific. 

The Territory of Alaska occupies an area of 550,000 
square miles. 

The Territory of Alaska is mainly mountainous. The 
shore lands of the Arctic are frozen moor-lands like the 
tundras of Asia. 

The Yukon and Kuskovim are the principal rivers. 

Myriads of salmon visit the rivers during the breeding 
season. 

Valuable food-fish are found in the waters off the coasts. 

Numerous fur-bearing animals are found in Alaska- 



GENERAL REVIEW QUESTIONS. 



oXKo 



Mathematical Geography. 

What is the earth's position in the solar system ? 

How much larger is the sun than the earth? 

Of what use are latitude and longitude ? 

Distinguish between a map of the earth on a Mercator's 
projection, and maps on equatorial and polar and conical 
projections. 

Explain the cause of the change of day and night. 

Explain the causes of the change of seasons. 

The Land. 

Enumerate the proofs of the present heated condition 
of the interior of the earth. 

What is the theory for the exclusive occurrence of vol- 
canoes near the borders of the ocean? 

Why is it unnecessary to consider the interior of the 
earth as in a fluid condition like that of the lava ejected 
from volcanoes? 

Name the principal regions of active volcanoes. 

What facts have been discovered respecting earthquake 
shocks ? Why should the shocks occur more frequently at 
night than during the day, or during winter than summer ? 

Into what two classes may unstratified rocks be divided ? 

Explain the origin of coal. 

Enumerate some of the changes which are now taking 
place in the crust of the earth. 

What are the relative land- and water-areas of the earth ? 

Describe the land hemisphere. The water hemisphere. 

What do you understand by lines of trend? 

Which of the continents contains, in proportion to its 
area, the greatest length of coast line? Which the least? 

Distinguish between continental and oceanic islands; 
between coral and volcanic islands. 

Why does the presence of an atoll in any part of the 
ocean prove the subsidence of its bed at that point? Ex- 



plain the nature of the coral formations off the southern 
coast of Florida. 

What do you understand by the forms of relief of the 
land? 

Distinguish between a mountain and a hill. A plateau 
and a plain. 

What peculiarities are noticeable in the general relief 
forms of the continents? 

Which of the continents resemble each other in the gen- 
eral arrangement of their relief forms ? In what respect 
do they all resemble one another? 

The Water. 

Enumerate the principal uses of water in the economy 
of the earth. 

What effect has the high specific heat of water on the 
climate of maritime countries? 

What is the cause of the heat developed during the con- 
densation of a mass of vapor ? 

Distinguish between subterranean and surface drainage. 

Explain in general the origin of springs. 

Into what different classes may springs be divided ac- 
cording to the size of their reservoirs? According to 
the shape? The location? The shape of the outlet 
tube? 

Define calcareous, silicious, sulphurous, chalybeate, brine, 
and acidulous springs. 

Define river-system, basin, water-shed, source, channel, 
and mouth. 

Explain the origin of waterfalls. 

By what are the inundations of rivers caused? 

What is silt? In what different parts of a river-system 
may sift be deposited ? Define fluvio-marine formations. 

In what respects do tbe drainage-systems of North and 
South America resemble each other? 



GENERAL REVIEW QUESTIONS. 



167 



In what respects do the river-systems of Africa resemble 
those of the Americas? 

Why are the waters of lakes with no outlets generally 
salt? 

Name the great fresh-water lake-systems of the world. 

State the composition of ocean-water. What is its 
density? Its boiling-point? Its color? 

How do the five oceans compare with one another in 
area? 

Distinguish between inland seas, border seas, and gulfe 
and bays, and fiords. 

What facts are known respecting the shape of the bed of 
the Atlantic Ocean ? Of the Indian Ocean ? Explain the 
origin of the ooze-deposits on the ocean's beds. 

By what are waves caused? Upon what does their 
height depend ? 

How are tides caused ? 

Distinguish between ebb, flood, spring, and neap tides. 

Where does the parent tidal wave originate? 

In what part of the ocean are tides the highest? 
Why? 

What are the main causes of constant oceanic currents ? 

In what respects do the currents in the three central 
oceans resemble one another? 

The Atmosphere. 

What is the composition of the atmosphere? 

By what instrument is the pressure of the atmosphere 
measured ? 

What proof have we that the greater weight of the at- 
mosphere lies within a few miles of the earth's surface? 

Define climate. Enumerate the circumstances which 
influence the climate of a country. 

Why are the vertical rays of the sun warmer than the 
oblique rays? 

In what different ways does the atmosphere *eceive its 
heat from the sun ? 

Explain the origin of winds. 

Why should the general direction of the atmospheric 
circulation be between the equator and the poles? 

Name the different wind zones of the earth. 

What is the origin of land and sea breezes? 

What resemblance do land and sea breezes bear to 
monsoons ? 

Describe some of the peculiarities of cyclones. 

What facts have been discovered in regard to the great 
storms of the United States ? 

Enumerate the circumstances upon which the rapidity 
of evaporation depends. 

State the general law for the occurrence of precipi- 
tations. 

Under what circumstances will a heavy deposition of 
dew occur? 

Name the primary forms of clouds. The secondary 
forms. 

Explain the peculiarities of the rainfall in each of the 
wind zones. 

Why is the rainfall on mountains heavier than that on 
plains? 

Define snow line. On what three circumstances does the 
height of the snow line depeud ? 

Describe the formation of a glacier. 



Enumerate the principal electrical and optical phenom- 
ena of the atmosphere. 

What is the probable cause of the earth's magnetism? 

Define volt, ohm, ampere. What analogies exist between 
the flow of water in a pipe and an electric current ? 

Plant Life and Animal Life. 

Why should the distribution of light, heat, and moisture 
form the best basis for the distribution of vegetation ? 

Define flora. Distinguish between the horizontal and 
the vertical distribution of vegetation. 

State the limits of each of the horizontal zones of 
vegetation. 

What is the characteristic feature of the flora of each of 
these zones ? 

State the conditions requisite for the existence of forests ; 
of prairies ; of steppes ; of deserts. 

Enumerate the principal cultivated plants of the torrid, 
temperate, and polar zones. 

Define fauna. 

Upon what is the existence of animal life dependent? 

What is the cause of the change noticed in the fauna in 
passing from the equator to the poles, or from the base to 
the summit of a high tropical mountain? 

Enumerate the characteristic tropical fauna ; the temper- 
ate fauna ; the arctic fauna. 

What is the characteristic peculiarity of the fauna of 
each of the continents? 

Enumerate the proofs of the probable unity of the 
human race. 

Name the portions of the world inhabited by each of the 
primary and secondary races. 

Minerals. 

Name the principal useful metals. 
Enumerate the most important natural fuels. 
In what parts of the world are valuable deposits of coal 
found ? 
Name the most importaut gold-fields of the earth. 

Physical Features of the United States. 

What is the area of the United States, exclusive of 
Alaska? 

Describe the surface structure of the. United States. 

Describe the drainage-systems of the United States. 

What are the causes of the difference in the temperature 
of the eastern and western coasts? 

Between what extremes of mean annual temperature are 
the United States included? 

In what wind zone is the United States situated? 

Name the four principal regions of vegetation. 

Enumerate the chief agricultural productions of the 
country. 

What large animals are found in the United States? 

Name the chief mineral productions. 

What is the area of Alaska ? 

What are the principal indentations of its coast? 

Name the principal islands, of Alaska. 

Describe the river-system of the Yukon. 

Name the principal trees of Alaska. Name its principal 
fur-bearing animals. Its principal food-fishes. 



168 



PHYSICAL GEOGRAPHY. 



GENERAL MAP QUESTIONS. 



oWK° 



Volcanoes and Earthquakes. 

Describe the volcanic districts of the Pacific Ocean. 

In what portions of these districts are volcanoes most 
numerous ? 

Describe the volcanic districts of the Indian Ocean. 

In what direction do most of the lines of fracture in 
this ocean extend? 

Describe the volcanic districts of the Atlantic. 

Where are submarine eruptions most numerous in this 
ocean? 

Describe the earthquake district of the Mediterranean 
Sea and Central Asia. 

What other portions of the world are especially liable to 
earthquake shocks ? 

Name the parts of the world shaken by the great earth- 
quake of Lisbon, in 1755. 

Oceanic Areas and River-Systems. 

What two oceans receive the drainage of the greatest 
areas of the continents'' 

State, from a careful inspection of the direction in which 
the principal river-systems flow, the direction of inclina- 
tion of the principal slopes of the continents. 

Observe that in most of the continents there is a long 
gentle slope and a short abrupt slope; state the general 
direction of each of these slopes. 

Locate the principal systems of inland drainage in each 
of the continents. 

Name the principal lakes and rivers belonging to the 
larger of these systems. 

Describe in general the river-systems of the Atlantic, or 
the rivers draining into the Atlantic. Describe the river- 
systems of the Pacific. Of the Indian. Of the Arctic. 

Enumerate the five largest rivers belonging to each of 
these river-systems. 

Name the principal rivers of the world which have delta 
mouths. 

What are the land and water boundaries of each of the 
five oceans ? 

Ocean Currents. 

What is the general direction of the equatorial ocean 
currents? Explain the cause of this general direction. 
What exception can you find to it ? 

What is the general direction of the Arctic currents ? Of 
the Antarctic curreuts? 

What are the causes of these general directions ? 

Describe the principal currents of the Atlantic ; of the 
Pacific; of the Indian Ocean. 

Locate the principal grassy seas. 

Explain the cause of these seas. 

Name the principal warm ocean currents ; the principal 
cold ocean curreuts. 

Name some cold currents which powerfully affect the 
climate of different parts of the earth ? Name some warm 
currents which powerfully affect the climate. 

In what respects do the general directions of the cur- 
rents in each of the central oceans resemble one another ? 

Name the points of resemblance between the Gulf 
Stream and the Japan Current. 



Isothermal Lines and Physical Zones. 

Point out the most striking deviations in the directions 
of the isothermal lines from the parallels of latitude. 

Explain in each case the main cause of these deviations. 

In what part of the world do the isothermal lines coin- 
cide most nearly with the parallels ? 

Trace on the map the isothermal line of 79° Fahr. Of 
32° Fahr. Of 40° Fahr. 

In what parts of the world is the highest temperature 
found during the month of July ? 

What is the temperature of the greatest cold of Jannary ? 
Where is it found ? 

What is the mean temperature of London for January ? 
For July? What other large cities have nearly the same 
mean July or January temperature as London ? 

What is the mean temperature of Bombay for January? 
For July? What other large cities have nearly the same 
mean July or January temperature as Bombay? 

Point out the northern limit of drift ice. The southern 
limit. 

Why is it advantageous for a vessel sailing from England 
or America via, the Cape of Good Hope to maintain an 
easterly direction both going and returning? 

Describe the boundaries of the physical torrid, tem- 
perate, and frigid zones. 

Name the principal countries which lie wholly or in part 
in each of these zones. 



Winds, Rain, and Ocean-Routes. 

State the boundaries of each of the wind zones. 

What is the general direction of the wind in each of 
these zones? 

Name the principal monsoon regions of the world. 

Enumerate the principal mountain and desert winds. 

What is the direction of the rotation of the wind in the 
cyclonic storms of the northern hemisphere? Of thesouth- 
ern hemisphere ? 

Name the principal storm-regions of the world. 

Describe the characteristic rainfall in each of the princi- 
pal wind zones. 

What would be the general route of a vessel in sailing 
from America to Europe, and back again ? From Europe 
to San Francisco ? 

What two sailing routes are there from Europe to Aus- 
tralia or India ? 

Vegetation. 

Give the boundaries of each of the plant zones. 

State the countries or portions of countries which lie in 
each of these zones. 

Name some of the useful plants of each of these zones. 

Point out on the map the northern limit of trees. The 
southern limit. 

Name the portions of the world from which valuable 
timber is obtained. 

What are the principal tea- and coffee-growing countries 
of the world ? 

Where are the principal forests ? 



GENERAL MAP QUESTIONS. 



169 



Animals. 

What limits are assumed as the boundaries of the tropi- 
ca], temperate, and arctic fauna? 

Name the principal tropica], temperate, and arctic 
fauna ? 

What domesticated animals are found in the tropical and 
temperate zones ? 

Trace on the map the northern limit of the camel and 
of the reindeer ; of monkeys. The southern limit of the 
camel ; of monkeys ; of the polar bear, and of the elephant 
and rhinoceros. 

In what parts of the world are the whale, seal, and wal- 
rus found ? 

Describe the limits of the grizzly bear. Of the musk-ox. 

What are the characteristic animals of the New World ? 
Of the Old World? 

State the characteristic fauna of North America. Of 
South America. Of Europe, Asia, Africa, and Australia. 

The Races of Men. 

Trace on the map the northern and southern limits of 
permanent habitation. 

Name all the countries of the world inhabited by the 
Caucasian race. 

In what parts of the world are the Caucasians mixed with 
other races ? 



Name the different countries of the world inhabited by 
the Mongolian race. 

Name some of the different peoples belonging to this 
race. 

What parts of the world are peopled by the Ethiopian, 
or Negro race ? 

Name some of the different tribes belonging to this race. 

Name the different countries of the world inhabited by 
the secondary races of men ? 

Give the names of the principal tribes of each of the 
secondary races. 

What different races of men inhabit North America? 
South America? Europe? Asia? Africa? Australia? 

Physical Map of the United States. 

Describe from the map the forms of relief of the United 
States. 

Name the principal mountain-ranges belonging to the 
predominant and secondary mountain-systems. 

Describe the drainage-systems of the United States. 

What large lake-system is situated in the north-eastern 
part of the United States ? 

Trace on the map the general directions of the principal 
isothermal lines, showing the hottest and coldest portions 
of the country. 

Name the principal islands which lie near the coasts of 
the United States. 

Name the fluvio-marine formations of the eastern coast. 



QUESTIONS RELATING TO THE PHYSICAL GEOGRAPHY 

OF A STATE. 



°&i<> 



In what physical region is this State principally situ- 
ated? 

Is the general surface of this State more or less than one 
thousand feet above the sea level? 

Into what body or bodies of water do the principal 
rivers of this State empty? 

Name the principal lakes located within, or that border 
on this State, if any. 

Name the principal rivers or river systems that are 
partly or wholly situated in this State. 

What is a navigable river? 

Name the navigable rivers of this State, if any. 

Name the navigable lakes in this State, or that border 
on the State, if any. 



Name the principal mountain system of this State, if 
any. 

Has this State any coast line ? If so, name its principal 
inlets, bays, harbors, points or promontories. Name the 
islands that lie near the coast, if any. 

What is the general climate of this State ? When is rain 
most common ? 

Name the cereals of this State. 

Name the principal fruits of this State. 

Name the other agricultural products of this State in 
addition to cereals and fruits. 

Are any wild animals found in this State ? 

Name the principal mineral products of this State. 





PRONOUNCING VOCABULARY- 



sounds OF THE LETTERS. 



Vowels. 
Fate, far, fill, fat, a (obscure), as in organ, oval; ah, inter- 
mediate between a and a, as in al-a-bah'-ma; aa or a long; 
me, wH, e, as in berth, ravel; pine or pine, pin, i, as in firm, 
evil ; n&, not, o, as in sermon, harbor ; oo, as in moon ; 65, as 
in good; 6w, as in now; u, as in tube; u, as in tub; u, the 
French eu, nearly like u in tub, or fur; y and ey, at end of 
unaccented syllable, like e in me ; ai and ay, like a in fate ; 
au and aw, as a in fall ; ee, as i in pit; ow or au, as now or our. 

Consonants. 
Th as in thin; th, as in this; D, as th, in this; G and 
K, sound of the German ch, somewhat like our h, strongly 



aspirated, E. indicates a blending of the sounds of n and y; 
I, a blending of 1 and y ; m and n and s G , nasal, like our ng ; 
r, like rr in terror ; w, like our v. Pronounce all other letters 
as in English. 

The primary or principal accent is marked thus ('); the 
secondary, thus ( v ). 

In determining the correct pronunciation of a word, first 
sound the separate syllables distinctly, repeating the process 
several times; afterward pronounce the whole word smoothly 
and continuously, being careful to' mark the accents; e.g. 
Nevada, na-va'-da, nay-vah'-dah; Apache, a-pa'-cha, ah- 
pah'-ebay; Canada, kan'-a-da, kan'-uh-duh. 



A. 

Abyssinia, ab-is-sin'-e-a. 

Aconcagua, a-kon-ka'-gw4. 

Adelsberg, S/-dels-b5rg\ 

Adriatio, ad*-re-at'-ic. 

Afghanistan, 3,f-gS,n v -is-tan'. 

Agulhas, a-gool'-yas. 

Alabama, al-a-bab'-ma. 

Alaska, al-as'-ka. 

Albemarle, al-be-marl'. 

Aleutian, a-lu'-she-an. 

Algiers, al-jeerz'. 

Allegbanies, al-le-ga'-nees. 

Altamaha, al-ta-ma-haw'. 

Amazon, am'-a-zon. 

Amboyna, llm-boi'-na. 

Amoo, a-moo'. 

Amoor, i-moor'. 

Anabuao, 3,n-4-waek'. 

Anatolia, an-a-to'-le-a. 

Anticosti, an-te-kos'-tee. 

Antilles, an v -teel'. 

Antisana, an-te-sa'-ni. 

Appalaohicola, np'-pa-lah'-ehe-ko'-la. 

Apennines, ap'-en-nlnz\ 

Appalachian, ap-pa-la'-ehe-an. 

Apsheron, ap-shi-ron'. 

Ararat, ar'-a-rat\ 



Arohangel, ark-an'-jel. 
Arequipa, a-ra-kee'-pa. 
Arizona, ar*-i-zo'-na. 
Arkansas, ar-kan'-sas. 
Armenia, ar-mee'-ne-a. 
Arveiron, aiO-vi-ron'. 
Asia, a'-she-a, not i'-zhe-a. 
Atacama, a-tH-ka'-ma. 
Athabasca, ath'-a-bas'-ka. 
Auckland, awk'-land. 
Auvergne, o^-vairfi'. 
Azores, az'-ors, or az-orz'. 
Azov, az'-ov\ or a-zov'. 



B. 

Babylonian, bab-e-lo'-ne-an. 

Bahamas, ba-ha'-ma. 

Baikal, bi'-kal. 

Baku, ba^-koo'. 

Balkan, bal-kan'. 

Balkash, bal v -k4sh'. 

Baltimore, bawl'-te-more, or bawlt'-e- 

mor. 
Banda, ban'-da. 
Barbadoes, bar-bi'-doz. 



Batavia, ba-ta'-ve-a. 

Baton Rouge, bat'-on-roozh. 

Bedouins, bed'-oo-inz. 

Beled-el-Jerid, bel'-ed-el-jer-eed'. 

Beloochistan, bel-oo'-cbis-tin'. 

Belor, or Bolor, b6-lor\ 

Bengal, ben-gawl'. 

Berlin, ber'-lin. 

Bermudas, ber-moo'-daz. 

Bernina, ber-nee'-nl. 

Bohemian, bo-hee'-me-an. 

Bolivia, bo-liv'-e-a. (Spanish pron., 
bo-lee'-ve-i.) 

Bombay, bom-ba'. 

Boothia Felix, boo'-the-i fe'-liks. 

Bourbon, bur'-bon. 

Brahmapootra, brah'-ma-poo'-tra. 

Brazos, brah'-zos. 

Buenos Ayres, bo'-nos a'-riz, or bo'- 
nos airz. (Spanish pron., bwa'-noce 
I'-res.) 



c. 

Cairo, kl'-ro. 
Calabria, ka-la'-bre-a. 
Calcutta, kal-kut'-ta. 
Cambodia, kam-b6'-de-a. 



170 



fite, far, fall, fit, me, met, pine, pin, no, n5t, organ, berth, firm, sermon, tube, tub, thin, THis. 



PRONOUNCING VOCABULARY. 



171 



Cambridge, kame-brij'. 


F. 


J. 


Cameroons, cain-er-oons'. 






CantaDrian, kan-ta'-bre-an. 


Falkland, fawk'-land. 


Jamaica, ja-m&'-ka. 


Canton, kan-ton'. 


Fayal, fi-41'. 


Jan Mayen, yan-inl'-en. 


Cape Verde, verd'. 


Feejee, fee'-jee. 


Japan, ja-pan'. 


Caribbean, kar v -rib-bee'-an. 


Fezzan, feV-zan'. 


Java, ja'-va, or jah'-va. 


Carpathian, kar-pa'-the-an. 


Finsteraarhorn, fins'-ter-aar-horn. 


Jorullo, ho-rool'-yo, or ho-roo'-yo. 


Castile, kas-teel'. 


Flores, flo'-rSs. 




Cauca, kow'-ka. 


Formosa, for-ino'-sa. 




Caucasus, kaw'-ka-stis. 


Fusi Yama, fu-si-ya-ma'. 


K. 


Cayenne, ka-yenn', or kr-enn'. 






Celebes, sel'-e-bes. 




Kaffa, kaf -fa. 


Ceram, se-rani'. 


Gr. 


Kalahari, kal-a-ha'-re. 


Cevennes, sa v -venn'. 




Kamtchatka, kam-chat'-ka. 


Ceylon, see'-lon, or sil-on'. 


Gairdner, gard'-ner. 


Earakorum, ka*-ra-ko'-rum. 


Chagos, cha'-g&s. 


Gallapagos, ga-la'-pa-goce. 


Kenia, ke'-ni-a. 


Chamouni, shi'-moo-nee' (or Chamo- 


Ganges, gan'-gez. 


Kentucky, k3n-tuk'-ee. 


nix, sha x -mo-nee'). 


Gardafui, gar'-da-fwee'. 


Kerguelen, kerg'-e-len. 


Champlain, sham-plane'. 


Garonne, ga'-ronn'. 


Keweenaw, ke-wee'-naw. 


Charleston, charlz'-ton. 


Gaudaloupe, gwa-da-loo'-pi. 


Kilauea, ke v -16'-a-a. 


Chelyuskin, chel-yus'-kin. 


Ghauts, gawts. 


Kilimandjaro, kil v -e-man\ja-ro'. 


Chicago, she-kaw'-go. 


Gila, heel'-a. 


Kinghan, kin-gan'. 


Chili, ohil'-lee. 


Gilolo, je-Io'-lo. 


Kiolen, ky-6'-len, or chft'-len. 


Colima, ko-Iee'-ma. 


Greenwich, grin'-idge. 


Kodiak, ko'-de-ak. 


Colorado, kol-o-rah'-do. 


Grenada, gren-a'-da. 


Kong, k6ng. 


Como, ko'-mo. 


Grenelle, greh^-nell'. 


Kosciusko, kos-se-us'-ko. 


Comorin, com'-6-rin. 


Guadeloupe, gaw'-da-loop', or ga-deh- 


Kuen-lun, kwenMoon'. 


Comoro, kom'-o-ro. 


loop'. 


Kunchinjunga, koon-chin-jung'-ga. 


Congo, kong'-go. 


Guadiana, gwa-'le-a'-na. 


Kurile, koo'-ril. 


Constance, kon-stlnts'. 


Guardafui, gw;ir-da-fwee'. 




Cosiguina, ko-se-ghee'-nl. 


Guiana, ghe-a'-na. 






Guinea, ghin'-nee. 


L. 

Laccadive, lak'-ka-dlv\ 


D. 


H. 


Ladoga, la'-do-ga. 






Ladrones, lad-ronz'. 


Dakota, da-ko'-ta. 


Halle, hal'-leh. 


Lapland, lap'-land. 


Danube, dan'-ube. 


Hartz, haRts. 


La Puebla, la pweb'-la. 


Deocan, dSk'-kan. 


Havana, ha-van'-a. 


Lauterbrunnen, low'-ter-bro5n v -nen. 


Demavend, dem'-a-vend'. 


Hawaii, ba-wi'-ee. 


Lima, Iee'-ma. 


Detroit, de-troit'. 


Hayti, ha'-tee. 


Limpopo, Iim-p6'-p6. 


Dhawalaghire, da-wftr-a-gher'-ree. 


Heola, hek'-la. 


Llanos, l'ya'-nos. 


Dinaric, de-nar'-ic. 


Himalaya, him-a-la'-ya, or him-a'-la- 


Llullayacu, l'yoo-ryl-l'ya'-k&. 


Dnieper, nee'-pr. 


ya. 


Loffoden, lof-fo'-den. 


Dniester, nees'-ter. 


Hindoo-Koosh, hin'-doo-koosh. 


Loire, lwar. 


Dra, dra. 


Hindostan, hin^-do-stan'. 


Lombardy, lom'-bar-de. 


Duna, dil'-na. 


Hoang-Ho, ho-ang'-ho', nearly whang v - 


Loo Choo, loo'-chew'. 


Dwina, dwl'-na, or hwee'-na. 


ho\ 


Louisiana, loo-ee-ze-ah'-na. 




Hoogly, hoog'-lee. 


Louisville, loo'-is-vil, or Ioo'-e-vil. 




Humber, hiim'-ber. 


Lowell, lo'-el. 




Hungarian, hung-ga'-re-an. 


Lupata, lu-pa'-ta. 


E. 






Ecuador, Sk-wa-dor'. 


I. 


M. 


Edgecumbe, ej'-kum. 


Edinburgh, Sd'-in-bur-rDh. 


Iberian, T-bee'-re-an. 


Macao, ma-kow ; , or ma-ka-o. 


Elbe, Sib. (Ger. pron., eT-beh.) 


Ilaman, or Illimani, eef-ya-ma'-ne. 


Mackenzie, mak-k&n'-zee. 


Elbruz, eT-brooz\ 


Illinois, ir-lin-oi'. 


Madagascar, inad v -a-gas'-kar. 


Elton, eT-ton'. 


Indiana, in*-de-an'-a, or in-de-ah'-na. 


Madeira, mit-dee'-ra, or mi-da'-ra. 


Euphrates, u-fra'-tez. 


Indianapolis, in-de-an-ap'-o-lis. 


Madrid, mi-drid'. (Spanish pron-, uia 


Everest, eV-er-est. 


Iowa, i'-o-wa. 


dreed'.) 


Eyre, air. 


Irrawaddy, ir*-ra-wad'-de. 


Magdalena, mag- da-lee'- na. 



fate, far, fall, fat, me, met, pine, pin, no, n5t, organ, berth, firm, sermon, tube, tub, thin, this. 



172 PRONOUNCING VOCABULARY. 


Maggiore, mad-jo'-ri. 


P. 


San Joaquin, san no-a-keen', almost 


Malacca, ma-lak'-ka. 




wah-keen'. 


Malay, ma- la'. 


Pamir, pa-meer'. 


Santa Barbara, sin'-ta baR-ba-ra. 


Maldive, nial'-div. 


Famlico, pam'-lee-ko. 


Santa Cruz, san'-ta kroos. 


Manitoba, man-e-to'-ba. 


Pampas, pam'-pas. 


Santorini, san-to-ree'-nee. 


Mantchooria, rnan-choo'-re-a. 


Panama, pln-a-ma'. 


Sarmiento, saR-me-en'*to. 


Maracaybo, ma-ra-ki'-bo. 


Papua, pap'-oo-a. or pa v -poo'-a. 


Saskatchewan, sas-katch'-e-won. 


Marietta, ma-re-eY-ta. 


Paraguay, pa-ra-gwa', or pa-ra-gwl'. 


Scandinavian, skan-de-na'-ve-an. 


Marquesas, maR-ka'-sas. 


Paramaribo, par'-a-mar'-e-bo. 


Seine, Ban, or sen. 


Marseilles, mar-salz'. 


Pasoo, pas'-ko. 


Senegal, sen'-e-gawl'. 


Mauna Loa, mow'-na lo'-a. 


Patagonian, pata-go'-ne-an. 


Shasta, shas'-ta. 


Mauritius, maw-rish'-e-us. 


Paumotu, pow-m6-too'. 


Siam, si-am', or se-am'. 


Mediterranean, ined v -e-ter-ra'-ne-an. 


Peling, pa* -ling'. 


Sicily, sis'-il-e. 


Melbourne, mel'-burn. 


Persian, per'-she-an. 


Sierra Estrella, Be-eV-Rl 4s-treT-ya. 


Mesopotamia, mes v -o-po-ta'-me-a. 


Petchora, petch'-o-ri. 


Sierra Leone, se-er'-ra le-o'-nee. 


Michigan, mish'-e-gan, formerly mish- 


Philippine, fil'-ip-pin. 


Sierra Madre, se-eV-Ra ma'-nra. 


e-gan'. 


Platte, platt. 


Sierra Nevada, se-eV-ra na-vi'-ua. 


Mississippi, mis^-sis-sip'-pee. 


Polynesia, por-e-nee'-she-a. 


Singapore, sing'-ga-pore'. 


Missouri, mia-soo'-ree. 


Pompeii, pom-pa'-yee. 


Sir, or Sihon, sir, or Eeer, 6ee'-hon'. 


Mobile, mo-beel'. 


Pontohartrain, pont-ehar-tran'. 


Sitka, sit'-ka. 


Moluccas, mo-luk'-kaz. 


Popocatepetl, po-po-ka-ta-petl'. 


Spitzbergen, spits-berg'-en. 


Monte Bosa, mon v -ta-r6s'-s£. 


Prussia, prush'-ya, or proo'-she-a. 


Steppes, steps. 


Mont Blanc, mon«-bI6n6'. 


Pyrenees, plr'-en-eez. 


St. Louis, sent loo'-is, or sent loo'-ee. 


Moosehead, moos v -hed'. 




St. Petersburg, sent pee'-terz-burg. 


Moscow, mos'-ko. 




St. Boque, sent rok'. 




Q. 


St. Thomas, sent tom'-as. 




Stromboli, strom'-bo-le. 


N. 


Quebec, kwe-b£k'. 
Quito, kee'-to. 


Sumatra, soo-ma'-tra. 
Sumbawa, soom-baw'-wa. 


Nanling, nan v -ling\ 




Suez, soo'-ez. 


Natchez, natch'-iz. 




Suliman, or Suleiman, son-14-man'. 


Netherlands, nem'-er-landz. 


R. 


Syracuse, slr'ra-kuz. 


Neusalzwerk, noi'-salts-verk. 


Syria, slr'-e-a. 


Nevada de Sorata, ne-vah'-da da so- 

ra'-ta. 
Newfoundland, nu' -fond-land'. 
Ngami, n'ga'-mee. 


Badack, ra'-dak. 




Baliok, ra'-lik. 
Beading, red'-ing. 
Rhine, rln. 


T. 

Tahitian, ta-hee'-tee-an. 


Niagara, nl-ag'-a-rah, originally ne- 
a-ga'-ra. 


Bhone, ron. 


Tanganyika, tin-gan-ye'-ka. 


Biobamba, re-o-bam'-ba. 


Tarim, ta'-rem. 


Nioaragua, nik-ar-a'-gwa. 


Bio de la Plata, ree'-o da la pla'-tl. 
Bio Grande, ree'-o gran'-da. 


Tasmania, taz-ma-ne-a. 


Niemen, nee'-men. 


Taurus, taw'-rus. 


Nieuveldt, nyuw'-velt. 
Niger, nl'-ger. 


Bio Janeiro, ri'o ja-nee'-ro. 


Tohad, chad. 


Boanoke, ro v -an-5k'. 


Teneriffe, teV-er-iff'. 


Norfolk, nor'-f9k. 

Nova Scotia, no'-va sko'-she-a. 

Nova Zembla, no'-va zem'-bla. 


Rodriguez, ro v -dreeg'. 
Bussia, riish'-i-a, or roo'-she-a. 


Thames, temz. 
Thian-Shan, tee*-an'-shan. 


Bussian Amerioa, roo'-shan a-meV- 


Thibet, tib'-et, or tib-et'. 


Nubia, nu'-be-a. 








e-ka. 


Timor, te-mor'. 


N'yassa, or Nyassi, ne-as'-see. 




Titicaca, te-te-ka'-ka. 
Tocantins, to-kan-teens'. 




s. 


Toledo, to-lee'-do. (Spanish pron., to- 


o. 




la'-Do.) 




Sabine, sa-been'. 


Tongan, tong'-gan. 


Obe, o'-bee. 


Saghalien, sa-ga-lee'-an, or sa-ga- 


Torrens, tor'-rens. 


Okeflnokee, o'-ke-fin-o'-kee. 


leen'. 


Torres, toR'-RSs. 


Okhotsk, o-Kotsk'. (Russian pron., 


Sahara, sa-ba'-ra, or sa'-ha-ra. 


Transylvanian, tran-sil-vi'-ne-an. 


o-Hotsk'.) 


Saint Helena, sant hel-ee'-na. 


Trieste, tre-Sst'. 


Onega, o-na'-ga. 


Salina, sa-li'-na. 


Trinidad, trin'-e-dad'. 


Onimak, oo-ne-mak'. 


Salzburg, salts'-burg. 


Tristan d'Acunha,tris'-tan da-kun'-yl. 


Ontario, on-ta'-re-o. 


Samoan, sam-o'-an. 


Tundras, toon'-dra. 


Oregon, or'-e-g9n. 


Sandwich, sand'-wich, or sand'-wij. 


Tunis, tu'-niss, or too'-niss. 


Orinoco, or-e-no'-ko. 


San Francisco, san fran-sis'-ko. 


Turkestan, tooR'-kis-tin'. 


fate, far, fall, fat, me, m 

I 


8t. pine, pin, nA, not, organ, berth, firm, sern 


190, tube, tub, thin, mis. 



PRONOUNCING VOCABULARY. 



u. 


w. 


Yaktusk, yV-kootsh\ 


Tang-tse-Kiang, yang^-tse-ke&ng'. 


TJrumiyah., oo-roo-mee'-ya 


Wabash, waw'-bash. 


Yeddo, yed'-do. 




Wasatch, wa'-saoh. 


Yellowstone, yel'-lo'-stone. 




Wener, w&'-ner. 


Yenisei, ydn^-e-sa'-e, or ySn^-e-say'. 




Weser, we'-zer. (Ger. pron., wi'-zer.) 


Yosemite, yo-sem'-e-te. 


V. 


West Indies, west in'-deez. 


Yucatan, yoo-ka-tin'. 


Wetter, wet'-ter. 


Yukon, yu'-kon. 


Valdai, val'-di. 


Winnebago, win v -ne-ba'-go. 




Vancouvers, van-koo'-vers. 


Winnipeg, win'-e-peg. 




Venezuela, veV-Sz-wee'-la. 


Wisconsin, wis-kon'-sin. 




Vesuvius, ve-su'-vl-us. 


Worcester, woos'-ter. 


z. 


Viohy, vee v -shee'. 




Vienna, vS-en'-na. 




Zagros, za'-gros\ 


Vindhya, vlnd'-ya. 


Y. 


Zambezi, zam-ba'-zee. 


Volga, vol'-ga. 




Zealand, ze'-land. 


Vosges, vozh. 


Yabloni, ya-blo-noi'. 


Zurrah, zur'-ra. 



BRIEF ETYMOLOGICAL VOCABULARY. 



Amazon, " Boat destroyer." 

Arabia, " The land of the sunset." 

Brahmapootra, " The son of Brahma." 

Cameroons, "A shrimp." 

Deccan, " The south." 

Ecuador, " The equator." 

Elton, "Golden lake." 

Formosa, "Beautiful" (island). 

Gallapagos, " Islands of the tortoises." 

Ganges, " Heavenward flowing." 

Himalaya, " The abode of snow." 

Hindostan, "The country of the Hindoos," or " Negi'o- 

land." 
Hoang-Ho, " Yellow river." 
Holland, " Muddy or marshy land." 
Irrawaddy, " The great river." 
Java, "Bice." 
Labrador, "Cultivable." 
Ladrones, " Islands of the thieves." 
Lauterbriinnen, " Nothing but springs." 
Maldives, " Thousand islands." 



Mantchooria, " Country of the Mantchoos." 

Mer de glace, " Sea of ice." 

Mesopotamia, " Between the rivers." 

Mississippi, " The great water." 

Missouri, " Muddy water." 

Netherlands, " The low countries." 

Niphon, " Fountain or source of light." 

Nova Scotia, " New Scotland." 

Nyassa, "The sea." 

Orinoco, " The coiled serpent." 

Papua, " Frizzled hair." 

Patagonians, " Men with large feet." 

Polynesia, " Many islands." 

Popocatepetl, " Smoking mountain." 

Saskatchewan, " Swift current." 

Sierra Nevada, "Snow-clad mountain." 

Singapore, " City of the lion." 

Staubbach, " Dust or mist brook." 

Thian-Shan, "The celestial mountain." 

Winnipiseogee, "The smile of the great Spirit.' 

Yang-tse-Kiang, " Son of the great water." 




20 




Statistical Tables. 



Hydrographic Table of the Rivers of the 
World (from A. K. Johnstok). 



Name of River. 



Ehine 

Vistula . . . . 

Elbe 

Oder 

Niemen . . . . 

Seine 

Nile 

Danube . . . . 
Dnieper . . . . 

Obi 

Yenisei . . . . 

Lena 

Volga 

Sir or Sihon . . 

Amoor 

Yan g-tse-Kiang 
Hoang-Ho . . . 

Ganges 

Indus 

Euphrates . . . 
Irrawaddy . . 



Area of basin 

in geographical 

square miles. 



65,280 

56,640 

41,860 

?9,040 

32,180 

22,620 
520,200 (?) 
234,080 
169,680 
924,800 
784,530 
594,400 
397,460 
237,920 (?) 
582,880 
547,800 
537,400 
432,480 
312,000 (?) 
195,680 
331,200 



Length of 
stream includ- 
ing windings. 



Areas of the Principal Lakes of the 
Earth. (In English square miles.) 



NEW WOELD. 



St. Lawrence and Great Lakes 

Delaware 

Orinoco 

Amazon 

Tocantins 

San Francisco ...... 

La Plata 

Mississippi 

Eio del Norte 

Mackenzie . 

Saskatchewan 

Columbia 

Colorado 

174 



297,600 


1,800 


8,700 


265 


252,000 


1,352 (?) 


1,512,000 


3,080 


284,480 


1,120 


187,200 


1,400 


886,400 


1,920 


982,400 


3,560 


180,000 


1,840 (?) 


441,600 


2,120 


360,000 


1,664 


194,400 


1,360 


170,000 


800 (?) 



600 

520 

684 

480 

460 

340 
2,240 (?) 
1,496 
1,080 
2,320 
2,800 
2,400 
2,400 
1,208 (?) 
2,380 
2,880 
2,280 
1,680 
1,960 
1,492 
2,200 



America. 

Area sq. m. 

Superior 28,600 

Michigan 26,000 

Huron 20,400 

Great Slave 12,800 

Erie 9,600 

Winnipeg 9,600 

Georgian Bay .... 8,000 

Great Bear 8,000 

Ontario 6,300 

Maracaibo 4,900 

Titicaca 4,200 

Athabasca 3,000 

Nicaragua 2,800 

Great Salt 2,200 

Green Bay 2,000 

Champlain 480 

Pontchartrain . . . . 440 

Pyramid 360 

Moosehead 240 

Winnebago 212 

Eueope. 

Ladoga 6,330 

Onega 3,280 

Wener 2,136 

Wetter 839 

Malar 763 



Area, sq. m. 

Geneva 326 

Constance 290 

Maggiore 152 

Asia. 
Caspian Sea .... 160,000 

Aral Sea 88,000 

Baikal 13,000 

Balkash 8,600 

Zurrah(Afghanistan) 4,000 

Wan 2,200 

Urumiyah 1,800 

Lop 560 

Dead Sea 400 

Tiberias 200 

Africa. 

Victoria Nyanza . . 28,000 

Albert Nyanza . . . 26,000 

Tchad 15,000 

Tanganyika .... 13,000 

Nyassa 5,000 

Australia. 

Eyre 3,000 

Torrens 2,600 

Gairdner 2,400 



Population of the Earth. 

North America 89,250,000 

South America 36,420,000 

Europe 380,200,000 

Asia 850,000,000 

Africa 127,000,000 

Australia 4,730,000 

Polar Eegions 300.000 

Total 1,487,900,000 



STATISTICAL TABLES. 



175 



Tables showing the Area and Product 
of some of the Cereals, etc., in the 
United States. 



(From the Census Reports of 1890.) 
INDIAN COEN. 



State. Acres. 

Iowa 7,585,522 

Illinois 7,860,917 

Kansas 7,314,765 

Nebraska 5,480,279 

Missouri 6,069,638 

Ohio 3,189,553 

Indiana 3,586,190 

Kentucky 2,960,382 

Tennessee 2,791,324 

Pennsylvania . . . 1,252,369 

WHEAT. 

Minnesota 3,372,627 

California 2,840,807 

Illinois 2,239,861 

Indiana 2,570,017 

Ohio 2,269,585 

Kansas 1,582,635 

Missouri 1,946,785 

North Dakota .... 2,708,199 

Michigan 1,501,225 

Pennsylvania .... 1,318,472 



Bushels. 

313,130,782 

289,629,705 

259,574,568 

215,895,996 

196,904,915 

113,892,318 

108,843,094 

78,434,847 

63,635,350 

42,318,279 



52,300,247 
40,869,337 
37,371,081 
37,318,798 
35,559,208 
30,399,871 
30,113,821 
26,388,455 
24,771,171 
21,595,499 



Iowa , 

Illinois 3,848,897 

Wisconsin 1,627,151 

Minnesota 1,579,258 

Kansas 1,463,526 

Nebraska 1,503,515 

Ohio 1,215,355 

Missouri 1,676,706 

New York 1,417,371 

Michigan 1,085,759 



OATS. 

3,752,141 146,679,289 

, . . . 137,602,804 

... 60,739,052 

.... 49,958,791 

. . . 44,629,034 

. . . 43,843,640 

. . . 40,136,732 

. . . 39,820,149 

. . . 38,896,479 

. . . 36,961,193 



California . . . 
Wisconsin . . . 

Iowa 

Minnesota . . 
New York . . 
Michigan . . . 
Nebraska . . . 
North Dakota . 
Washington . . 
Illinois .... 



Wisconsin . . 
Pennsylvania . 
New York . . 
Kansas .... 
Illinois .... 
Michigan . . . 

Iowa 

Minnesota . . 
Nebraska . . . 
Ohio 



BAELEY. 

815,995 

474,914 

518,729 

358,510 

349,311 

99,305 

82,590 

109,339 

51,551 

41,390 

EYE. 

275,058 

336,041 

236,874 

199,146 

165,589 

140,754 

93,707 

62,869 

81,372 

59,643 



BUCKWHEAT. 



New York . . 
Pennsylvania . 
Wisconsin. . . 
Michigan . . . 
Maine .... 
Iowa .... 
Minnesota . . 
Vermont . . . 
Ohio 



West Virginia . 



280,029 
210,488 
77,458 
70,046 
22,395 
25,243 
22,090 
13,429 
14,052 
13,696 



17,548,386 
15,225,872 
13,406,122 
9,100,683 
8,220,242 
2,522,376 
1,822,111 
1,569,167 
1,269,140 
1,197,206 



4,250,582 
3,742,164 
3,065,623 
2,917,386 
2,627,949 
2,101,713 
1,445,283 
1,252,663 
1,085,083 
1,007,156 



4,675,735 
3,069,717 
1,064,178 
811,977 
466,411 
286,746 
281,705 
271,216 
162,833 
120,469 



Slate. 
Kentucky. . . 
Virginia . . . 
Tennessee . . 

Ohio 

North Carolina 
Pennsylvania . 
Indiana .... 
Maryland . . . 
Missouri . . . 
Wisconsin. . . 



TOBACCO. 

Acres. Pounds. 

323,409 283,300,000 

127,052 64,034,000 

67,119 45,641,000 

39,105 35,195,000 

57,107 25,755,000 

19,500 24,180,000 

18,252 16,153,000 

33,775 14,017,000 

14,126 13,109,000 

13,813 12,846,000 



Population of the United States. 

(From the Census of 1890.) 

North Atlantic States 17,401,545 

Maine 661,086 

New Hampshire 376,530 

Vermont 332,422 

Massachusetts 2,238,943 

Ehode Island 345,506 

Connecticut 746,258 

New York 5,997,853 

New Jersey 1,444,933 

Pennsylvania 5,258,014 

South Atlantic States 8,857,920 

Delaware 168,493 

Maryland 1,042,390 

District of Columbia 230,392 

Virginia 1,655,980 

West Virginia 762,794 

North Carolina 1,617,947 

South Carolina 1,151,149 

Georgia 1,837,353 

Florida 391,422 

North Central States 22,362,279 

Ohio 3,672,316 

Indiana 2,192,404 

Illinois 3,826,351 

Michigan 2,093,889 

Wisconsin 1,686,880 

Minnesota 1,301,826 

Iowa 1,911,896 

Missouri 2,679,184 

North Dakota 182,719 

South Dakota 328,808 

Nebraska 1,058,910 

Kansas 1,427,096 

South Central States lO^ ^ 

Kentucky 1,858,635 

Tennessee 1,767,518 

Alabama - 1,513,017 

Mississippi 1,289,600 

Louisiana 1,118,587 

Texas 2,235,523 

Indian Territory — 

Oklahoma 61,834 

Arkansas 1,128,179 

Western States 3,027,613 

Montana 132,159 

Wvoming 60,705 

Colorado 412,198 

New Mexico 153,593 

Arizona 59,620 

Utah 207,905 

Nevada 45,761 

Idaho 84,385 

Washington 349,390 

Oregon 313,767 

California 1,208,130 

Total population of the United States .... 62,622,250 



176 



STATISTICAL TABLES. 



Cities of the United States having a Pop- 
ulation over 30,000, in order of Pop- 
ulation. 

(From the Census of 1890.) 

NO. CITIES. POPULATION. 

1. New York City, N. Y 1,515,301 

2. Chicago, 111 1,099,850 

3. Philadelphia, Pa 1,046,964 

4. Brooklyn, N. Y 806,343 

5. St. Louis, Mo 451,770 

6. Boston, Mass 448,477 

7. Baltimore, Md 434,439 

8. San Francisco, Cal 298,997 

9. Cincinnati, 296,908 

10. Cleveland, 261,353 

11. Buffalo, N. Y. 255,664 

12. New Orleans, La 242,039 

13. Pittsburgh, Pa 238,617 

14. Washington, D. C 230,392 

15. Detroit, Mich 205,876 

16. Milwaukee, Wis 204,468 

17. Newark, N. J 181,830 

18. Minneapolis, Minn 164,738 

19. Jersey City, N. J 163,003 

20. Louisville, Ky 161,129 

21. Omaha, Neb 140,452 

22. Eochester, N. Y . 133,896 

23. St. Paul, Minn 133,156 

24. Kansas City, Mo 132,716 

25. Providence, E. 1 132,146 

26. Denver, Col 106,713 

27. Indianapolis, Ind 105,436 



NO. CITIES. POPULATION. 

28. Allegheny City, Pa 105,287 

29. Albany, N. Y 94,923 

30. Columbus, 88,150 

31. Syracuse, N. Y 88,143 

32. Worcester, Mass 84,655 

33. Toledo, 81,434 

34. Eichinond, Va 81,388 

35. New Haven, Conn 81,298 

36. Paterson, N. J 78,347 

37. Lowell, Mass 77,696 

38. Nashville, Tenn 76,168 

39. Scranton, Pa 75,215 

40. Fall Eiver, Mass 74,398 

41. Cambridge, Mass 70,028 

42. Atlanta, Ga 65,533 

43. Memphis, Tenn 64,495 

44. Wilmington, Del 61,431 

45. Dayton, 61,220 

46. Troy, N. Y 60,956 

47. Grand Eapids, Mich 60,278 

48. Beading, Pa 58,661 

49. Camden, N. J 58,313 

50. Trenton, N. J 57,458 

51. Lynn, Mass 55,727 

52. Lincoln, Neb 55,154 

53. Charleston, S. C 54,955 

54. Hartford, Conn 53,230 

55. St. Joseph, Mo 52,324 

56. Evansville, Ind 50,756 

57. Los Angeles, Cal 50,395 

58. Des Moines, la 50,093 



INDEX. 



«XK« 



[The references are to paragraphs. 



Acclimation, 343 
Acidulous Springs, 166 
Africa, 83, 84, 85, 86, 88, 135 to 140 
inclusive, 186, 191, 192, 354, 
358, 363 
Age of Coal Plants, 71, 75 
of Fishes, 71, 74 
of Invertebrates, 71, 73 
of Mammals, 71, 77 
of Man, 71, 78 
of Eeptiles, 71, 76 
Agones, 302 
Agricultural Productions of the 

United States, 408 
Alaska, 395, 423 to 431 inclusive 
Alluvial Flats, 178 

Plains, 104 
American Continental Islands, 91 
or Copper-colored Eace, 358, 364, 
367 
Andes Mountain System, 117 
Animal Life, 227, 339 to 367 inclusive, 
407, 429 



Animals of Africa, 354 

of Alaska, 429 

of Arctic Eegions, 348 

of Asia, 353 

of Australia, 355 

of North America, 350 

of South America, 352 

of Temperate Eegions, 347 

of Torrid Eegions, 346 

of United States, 407 
Antarctic Circle, 16, 27 

Ocean, 199, 205 
Aphelion, 24 
Aqueous Eocks, 66 
Archaean Time, 71 
Arctic Circle, 16, 27 

Ocean, 111, 188, 199, 205 
Areas of Continents and Islands, 89 
Artesian Wells, 162 
Articulation of Land and Water, 200 
Asia, 83, 85, 86, 88, 129 to 134 inclu- 
sive, 185, 192, 353, 358, 360, 362 
Asteroids, 7, 8, 24 
Astronomical Climate, 234 



Atlantic Ocean, 46, 47, 99, 188, 199, 

203, 216, 223 
Atmosphere, 79, 227 to 310 inclusive 
Atolls, 97, 100 
Aurora Borealis, 297 
Australasian Islands, 93 
Australia, 83, 84, 85, 86, 88, 141 to 

145 inclusive, 187, 192, a55, 366 
Australian Eace, 358, 364, 366 
Axis of a Mountain System, 106 

of the Earth, 13, 22, 27 
Azoic Age, 71, 72 

B. 

Barometer, 230 

Basaltic Columns, 62 

Basins of Eiver Systems, 168 

Bays, 200, 382 

Birds, 346, 347, 348, 352, 353, 355 

Birthplace of Tidal Wave, 212 

Bituminous Springs, 167 

Blue Color of the Sky, 308 

Boiling Point, 233 

Border Seas, 200 





INDEX. 


177 


Bore or Eager, 219 


Crevasses, 284 


Drainage, Subterranean, 154, 155, 157 


Breakers, 208 


Crust of the Earth, 35, 64, 79 


to 167 inclusive 


Building Stones, 370, 378, 422 


Crystalline Bocks, 67 


Surface, 154, 156, 168 to 193 in- 


Bunsen's Theory of Geysers, 164 


Currents of Antarctic Ocean, 223, 224 


clusive 




of Atlantic Ocean, 223 


Dunes or Sand-hills, 79 


c. 


of Indian Ocean, 225 


Dykes, 40, 62 


Calcareous Springs, 166 


of Pacific Ocean, 224 




Canons, 79, 389 


Cyclones, 254 to 257 inclusive, 401 


E. 


Carboniferous Age, 71, 75 




Earth, The, 5, 8, 13, 14, 15, 22, 24, 26, 


Caucasian Eace, 358, 359, 360, 361 


D. 


27, 30 to 35 inclusive, 301 


Cause of Change of Seasons, 27 


Darwin's Theory of Coral Islands, 101 


Earth's Axis, 22, 27 


of Deserts, 153, 278 


Day and Night, 23, 29 


Crust, 32, 35, 36, 64, 79 


of Earthquakes, 56, 58 


Dead Sea, 192 


Interior, Condition of, 33, 34 


of the Earth's Eevolution, 11 


Degrees of Latitude, 17, 19 


Heated, 32, 36 


of Heating Power of the Sun's 


of Longitude, 19 


Orbit, 24, 26, 27 


Bays, 235 


Deltas, 171, 178, 179 


Original Fluidity, 30, 31 


of Ocean Currents, 221 


Density of Water, 148, 149 


Eevolution, 11, 24, 27 


of the Saltness of Inland Waters, 


Depth of the Ocean, 201 


Eotation, 22, 221, 243 


192 


Deserts, 139, 153, 278, 329 


Shape, 13, 14, 30 


of the Saltness of the Ocean, 195 


Desert Winds, 251 


Earthquakes, 36, 50 to 63 inclusive, 


, of Volcanic Eruptions, 41, 42 


Detritus, 174 to 180 inclusive 


79 


Cenozoic Time, 71 


Devonian Age, 71, 74 


Eastern Continent, 83, 88, 104, 278 


Cereals, 331, 409 


Dew, 264, 267 


Hemisphere, 21, 83 


Chalybeate Springs, 166 


Diameter of the Earth, 13, 15 


Effects of Earthquakes, 63 


Changes in the Earth's Crust, 79 


Dimensions of the Earth, 15 


of Earth's Heated Interior, 36 


Change of Day and Night, 23 


Distribution of Animal Life, 340, 341, 


of Heat, 80, 314, 340 


of Seasons, 27 


342, 344, 407 


of Light, 80, 314 


Circles of the Earth, 16 


of Cereals, 331, 409 


of Maximum Density of Water, 


Circumference of the Earth, 15, 19 


of Continental Islands, 94 


149 


Classification of Minerals, 371 


of Coral Islands, 99 


of Moisture, 78, 80, 240, 314 


of Springs, 158 


of Earthquakes, 60 


of Ocean Waves, 79 


Climate, 30, 232 to 240 inclusive, 395, 


of Food Plants, 330 to 335 inclu- 


of Eunning Water, 79 


396, 397, 398, 427 


sive, 409, 411, 412 


of Eotation of the Earth on the 


Climatic Contrasts, 397 


of Glaciers, 287 


Winds, 243 


Clouds, 268, 269, 270 


of Grains used for Food, 331, 409, 


Elasticity of the Atmosphere, 228 


Coal, 75, 369, 370, 376, 417, 430 


412 


Electric Circuits, 290 


Oil, 167, 369, 370, 376, 419 


of Heat and Cold, 232 to 240 in- 


Potentials, 290 


Cold Springs, 161 


clusive, 340, 396 


Volts, 290 


Waves, 247; 401 


of Islands, 91 to 96 inclusive, 99 


Electricity, 290 to 304 inclusive 


Color of the Ocean, 196 


of Lakes, 190 


Eozoic Age, 71, 72 


Comets, 7 


of Land, 81 to 85 inclusive, 240 


Equator, 14, 16, 19, 20, 304, 317, 318 


Comparison of Belief Forms of Europe 


of Marine Animal Life, 340 


Equinox, March, 27, 211 


and Asia, 134 


of Metals, 414, 415, 416 


September, 27, 211 


Composition of the Atmosphere, 227 


of Minerals, 368, 413, 430 


Erosion, 79, 126, 169, 178, 208, 286, 368 


of the Earth's Crust, 64 


of Moisture, 240, 262 to 281 in- 


Estuary, 171, 219 


of Water, 146 


clusive, 340 


Etesian Winds, 251 


of Ocean Water, 194 


of Ocean Waters, 199 


Ethnography, 356 to 367 inclusive 


Constant Parallelism of the Earth's 


of Plants, 313 to 338 inclusive, 


Europe, 83, 85, 86, 88, 122 to 128 in- 


Axis, 27 


408 to 412 inclusive, 428 


clusive, 184, 191, 192, 358 


Springs, 159 


of Precipitation, 266 to 289 in- 


Evaporation, 262, 263 


Continents, 83, 86, 88, 102 to 145 in- 


clusive, 400 


F. 


clusive, 349 


of Eainfall, 272 to 278 inclusive, 


Continental Contrasts, 88 


399 


Falls of Niagara, Frontispiece, 169 


Drainage, 181 to 188 inclusive 


of Vegetation, 313 to 338 inclu- 


Fauna, 344 to 355 inclusive 


Islands, 89 to 94 inclusive 


sive, 402 to 406 inclusive, 408 


of Africa, 354 


Waters, 146 to 193 inclusive 


to 412 inclusive, 428 


of Arctic Zones, 348 


Contraction of the Earth's Crust, 79 


of Volcanoes, 48 


of Asia, 353 


Contrasts between Africa and Austra- 


of Water Areas, 190, 240 


of Australia, 355 


lia, 145 


of Winds, 240, 246 to 260 inclu- 


of North America, 350 


between Europe and Asia, 134 


sive, 399 


of South America, 352 


between North and South Amer- 


Division of Geological Time, 71 


of Temperate Zones, 347 


ica, 121 


Double Continents, 86 


of Tropical Zones, 346 


Coral Islands, 97 to 101 inclusive 


Dove's Law of Eotation of Winds, 247 


Features of Ocean Currents, 222 


Beefs, 100, 385 


Drainage, 154 to 193 inclusive, 283, 


Fiords, 126, 200, 286, 423 


Corona? and Halos, 309 


392, 393, 426 


Fiord Valleys, 108, 200 


Co-Tidal Lines, 213 


Inland, 189, 192, 393 


Fish, 346, 429 


Cradle of the Tides, 212 


Oceanic, 181 to 188 inclusive, 


Fluviatile Islands, 178 


Craters of Volcanoes, 38 


191, 392, 426 


Lakes, 178, 394 



178 



INDEX. 



Fogs, 268 

Food, 153, 339 

Plants, 331 to 338 inclusive, 408 
to 412 inclusive 

Foraminifera, 206 

Foraminiferal Land, 206 

Forests, 79, 172, 321, 322, 326, 351, 403, 
406 

Formation of Coal, 75 
of Coral Islands, 98 

Fossiliferous Rocks, 69 

Fossils, 68 to 71 inclusive 

Fragmental Rocks, 67 

Freezing Point, 233 

Fruits and Plants of Tropical Re- 
gions, 332, 333, 334, 336 
and Plants of Warm Temperate 
Regions, 334 

G. 

Gems, 379 
Geography, 1, 2, 3, 4 

Mathematical, 2 

Physical, 4 

Plant, 311 to 338 inclusive 

Political, 3 

Zoological, 339 to 355 inclusive 
Geological Time, 71 to 79 inclusive. 
Geysers, 49, 163, 164, 165 
Glacial Epoch of the Earth, 289 

Lakes, 286 
Glaciers, 161, 282 to 289 inclusive 
Great Basin, 389 

Circles, 16 

Circle of Illumination, 14, 23 

Interior Depression of Africa, 
139 

Low Plains, 109, 110, 113, 116, 
119, 122, 127, 129, 132, 141, 143, 
184 

Plains, 388 
Gulf Stream, 223, 261, 397 
Gulfs, 200, 382 

H. 

Hail, 279 

Halos and Corona, 309 

Harmattan, 251 

Heat, Effects of, 80, 314 

Energy of Water, 151 

of Water, 150 
Height of the Atmosphere, 231 

of Tidal Wave, 218 
Hemispheres, 16, 21, 83, 85 
High Lands, 103 
Hills, 103, 104 
Horizon, 14 
Horizontal Forms of the Land, 82 

Zones of Vegetation, 317 
Hot Desert Winds, 251 

or Thermal Springs, 161 
Human Race, 356 to 367 inclusive 
Hurricanes, 253, 255 
Hygrometer, 264 
Hypsometry, 231 

I. 

Ice, 282 to 288 

Icebergs and Icefloes, 288 



Igneous Rocks, 66 

Imaginary Circles, 16 

Inclination of the Earth's Axis, 27 

Indian Ocean, 46, 47, 99, 199, 204, 
215, 225,250 

Inertia, 5 

Influence of Destruction of Forests, 
172 

Inland Drainage, 189, 192, 393 
Seas, 200 

Insects, 352 

Interior of the Earth, 30 to 34 inclu- 
sive, 36 

International Weather Service, 401 

Inundations, 172 

Islands, 83, 90 to 101 inclusive, 178, 
383, 384, 424 

Isoclinal Lines, 304 

Isogonal Lines, 302 

Isolated Mountains, 107 
Oceanic Islands, 96 

Isothermal Lines, 238, 316, 396 



Jupiter, 8, 9 



Khamasin, 251 



K. 



Lagoons, 97 

Lakes, 178, 189 to 193 inclusive, 217, 

286, 392, 394 
Lake Systems of the United States, 

392, 393, 394 
Land and Sea Breezes, 248 

Hemispheres, 85 
Laplace's Hypothesis, 25, 31 
Latitude, 17, 19 
Lava, 39, 40, 41, 42, 43, 161 
Length of Day and Night, 29 
Light, Effects of, 80, 314 
Lightning, 253, 279, 293, 294, 295 

Rods, 295 
Lines of Trend, 87 
Llanos, 119, 318, 327 
Longitude, 18, 19 
Longitudinal Valleys, 108 
Looming, 310 
Low Lands, 103 
Lunar Tides, 210 

M. 

Maelstrom, 219 

Magnetic Attractions and Repulsions, 
299 

Equator, 304 

Needle, 298, 300, 302, 303, 304 

Properties of the Earth, 300 
Variations in, 302 

Storms, 302 
Magnetism, 298 

Origin of Earth's, 301 
Magnets, 298 

Malay or Brown Race, 358, 364, 365 
Mammalia, 346, 347, 348, 352, 353, 354 
Mangrove Islands, 384 



Map Projections, 20, 87 

Marine Plains, 104 

Mars, 8, 9 

Mathematical Zones, 28 

Maximum Density of Water, 143 

Meadows, 322, 328 

Mean Daily Temperature, 238 

Annual Temperature, 238 
Mer de Glace, 287 
Mercury, 8, 9 
Meridian Circles, 16, 17 
Meridians, 16 
Mesozoic Time, 71, 76 
Metals, 372, 414, 415, 4!6 
Metamorphic Rocks, 66 
Metamorphism, 66 

Meteorology, page 85, 227 to 310 in- 
clusive, 395 to 407 inclusive 
Meteors, 7, 10 
Mile, Geographical or Nautical, 19 

Statute, 19 
Milky Way, 12 
Mineral Springs, 166 
Minerals, 4, 368 to 379 inclusive, 413 

to 422 inclusive, 430 
Mirage, 310 

Mississippi Valley, 391, 400 
Modifiers of Climate, 240 
Moisture, 262 to 280 inclusive 

Effects of, 79, 80, 240, 314, 340 

Evaporation of, 262 
Mongolian Race, 358, 359, 362 
Monsoons, 249, 250, 275 
Moon, 7, 9, 209, 210, 211 
Moraines, 285, 286 
Mountain Knot, 106 

Passes, 106, 388 

Peaks, 106 

Ranges, 105, 106, 240 

Systems, 106, 107, 111, 112, 117, 
118, 123, 126, 130, 131. 137. 
138, 141, 142, 386, 387, 388, 389, 
390 

Winds, 252 
Mountains, 37, 38, 43, 102 to 145 in- 
clusive, 252, 277, 2S1, 286, 287, 
388, 389 
Movements of the Earth, 22 
Mud A'olcauoes, 49 

N. 

Names of the Planets. 8 
Natural Bridge, 390 

Gas, 369, 370, 376, 420 
Neap Tides, 211 
Negro Race, 358, 359, 363 
Neptune, 8, 9, 24, 25 
Neve 1 Region, 282 
Non-Fossiliferous Rocks, 69 
North America, 83, 85, 86, 87, 88, 110 

to 115 inclusive, 182, 191, 192, 

278, 350 
North-easterly Storms, 260 
North-east Trends, 87 
North-west Trends, 87 
Northern Continent. 46 

Hemisphere, 16, 21, 27, 29, 243, 

247, 250, 277, 303 





INDEX. 




179 


o. 


Plants, 4, 153, 311 to 338 inclusive, 


s. 




Oases, 139 


402 to 412 inclusive, 428 


Sahara Desert, 139, 251, 354 




Oblate Spheroid, 13 


Plateau of Brazil, 118 


Sailing Routes, 261 




Oblique Eays of Sun, 235 


of Guiana, 118 


Saint Elmo's Fire, 296 




Ocean, 194 to 226 inclusive 


Plateaus, 103, 105, 118, 126, 131, 139, 


Salt, 166, 194, 370, 377, 421 




Currents, 220 to 226 inclusive, 240 


277, 367 


Springs, 166, 421 




Waves, 79, 207, 208, 212, 214, 


Polar Circles, 16 


Samiels, 251 




218 


Prairies, 328, 351, 388, 404 


Saud Storms, 251 




Oceanic Areas, 199 


Precious Metals, 372, 414 


Sargasso Seas, 225 




Drainage, 181 to 188 inclusive, 


Precious Stones, 379 


Satellites, 7, 9, 10, 24 




191, 392, 426 


Precipitations, 265 to 289 inclusive, 


Saturn, 8, 9 




Islands, 95, 96 


400 


Sea and Land Breezes, 248 




Movements, 207 


Predominant Mountain Systems, 109, 


Seas, 200, 217 




Systems, 188 


110, 111, 116, 117, 122, 123, 124- 


Secondary Time, 71 




Ooze Deposits, 206 


129, 130, 136, 137, 141 


Mountain Systems, 109, 112, 


116, 


Optical Phenomena, 305 to 310 inclu- 


Pressure of the Atmosphere, 229 


118, 122, 126, 129, 131, 136 


138, 


sive 


Primary Time, 71 


141, 142 




Orbit of the Earth, 24, 26 


Prime Meridians, 18 


Selvas, 119, 352 




of Planets, 7, 25 


Prince Rupert's Drops, 57 


Shape of Bottom of Ocean, 198 




Orchids, 318 


Principal Oceanic Systems, 188 


of the Earth, 13, 14, 30 




Origin of Atmospheric Circulation, 


Prolate Spheroid, 13 


of the Earth's Shadow, 14 




242 


Proofs of the Earth's Original Fluid- 


of the Horizon, 14 




of Earth's Magnetism, 301 


ity, 30 


Sierra Nevada and Cascade Mountain 


of Rocks, 65 


of the Earth's Present Heated 


System, 111 




of Saltness of the Ocean, 195 


Interior, 32 


Silt, 174 to 180 inclusive 




of Swamps, 180 


of the Shape of the Earth, 14 


Silurian Age, 71, 73 




of Winds, 241 


Properties of Water, 147 


Simoons, 251 




Orology, 107 




Sirocco, 251 






Q. 


Sky, 307, 308 




P. 


Slaty Cleavage, 107 . 




Quaternary Age, 71, 78 


Small Circles, 16 




Pacific Mountain System, 111, 387 




Snow, 280, 281, 282, 283 




Ocean, 46, 47, 63, 199, 202, 214, 




Line, 281, 282 




224 


R. 


Solano, 251 




Palaeontology, 70 


Races of Men, 356 to 367 inclusive 


Solar System, 7, 12 




Palaeozoic Time, 71 


Primary, 358 


Tides, 210 




Pampas, 119, 320, 327 


Secondary, 364 


Solfataras, 49 




Parallels, 16 


Rafts, 177 


Solstice, Summer, 27 




Paraselense, 309 


Rain, 271 to 278 inclusive, 400 


Winter, 27 




Parhelia, 309 


Zones, 273, 276 


Solvent Powers of Water, 152 




Peculiarities in the Distribution of 


Rainbows, 306 


Soudan, 139 




Land Areas, 84 


Rainless Districts, 278 


Sounds, 180 




in Distribution of Volcanoes, 48 


Rapids, 169 


accompanying Earthquakes, 


54 


of Coast Lines, 88 


Regions of Perennial Rain, 276 


Source of Deep-seated Waters, 161 


of Continental Islands, 94 


of Perpetual Snow, 281, 282 


South America, 83 to 88 inclusive, 


of Continental Relief Forms, 109 


of Volcanoes, 46 


116 to 121 inclusive, 183, 


192, 


of Craters of Volcanoes, 38 


Relative Areas of Continents and 


278, 352 




of Cyclones, 257 


Islands, 89 


Southern Continent, 46 




of Glaciers, 284 


Relief Forms of the Land, 102 to 


Hemisphere, 16, 21, 27, 29, 


243, 


Peat Bogs, 369, 376, 418 


145 inclusive 


247, 250, 277 




Pele's Hair, 39 


Forms of the Continents, 110 to 


Specific Gravity, 15 




Peninsulas, 125, 131 


145 inclusive 


Heat of Water, 150 




Perihelion, 24 


Reptiles, 346, 347, 352, 353 


Spheroids, 13 




Periodical Springs, 160 


Reservoirs of Springs, 158 


Spring Tides, 211 




Petrifactions, 68 


Revolution of the Earth, 11, 24, 27 


Springs, 157 to 167 inclusive 




Petroleum, 167, 370, 376, 419 


River Basin, 168 


Stars, 6 




Springs, 167 


Channel, 168 


Steppe Lakes, 192 




Phases of the Moon, 211 


Courses, 169, 170, 174, 175, 178 


Rivers, 192 




Physical Climate, 234 


Mouths, 168, 171 


Steppes, 327, 405 




Zones, 239, 395 


Source, 168 


Stratified Rocks, 67 




-Plains, 103, 104, 111, 132, 388, 391 


Systems, 168, 182, 183, 184, 185, 


Storm Signals, 401 




Planetoids, 7 


186, 392 


Storms, 250, 251, 253 to 260 inclusive, 


Planets, 7, 8. 9, 10, 24 


Rivers, 168 to 188 inclusive 


302, 401 




Plant Geography, 311 to 338 inclu- 


Rocks, 30, 32, 64, 65, 66, 67, 69, 71 


Subterranean Drainage, 154, 155 


157 


sive 


Rocky Mountain System, 111, 388 


to 167 inclusive 




Life, 227, 311 to 338 inclusive, 


Rotation of the Earth, 22, 210, 221, ^ 


- Sulphurous Spriugs, 166 




402 to 412 inclusive, 428 


243 


Sun, 8, 10, 210, 234, 235, 236, 237 




Regions, 325 to 328 inclusive 


of the Winds, 247 


Sunset Tints of Sky, 307 





180 



INDEX. 



Surface Drainage, 154, 156, 168 to 193 

inclusive 
Structures of the Continents, 110 

to 145 inclusive 
Swamps, 180 

T. 

Temperature of the Atmosphere, 233 
to 240 inclusive 

of the Ocean, 197 
Temporary Springs, 159 
Tertiary Age, 71, 77 
Texas Northers, 250 
Thermometer, 233 
Thunder, 253, 279, 293 
Tidal Races, 219 

Waves, 210 to 219 inclusive 
Tides, 207 to 219 inclusive 

in Inland Waters, 217 
Tornadoes, 258, 401 
Trade Winds, 246, 249 
Transporting Power of Glaciers, 285 
Transverse Valleys, 108, 388 
Tropic of Cancer, 16, 27, 346 

of Capricorn, 16, 27, 346 
Tropics, 16, 27, 346 
Tufa, 39 

Tundras, 132, 323 
Typhoons, 255 

u. 

Undulating Plains, 104 

United States, 380 to 431 inclusive 

Unity of the Human Pace, 357 

Unstratifled Rocks, 67 

Uranus, 8, 9, 24 

Utility of Lakes, 193 

of Mountains, 102, 106 

of Ocean Currents, 226 

of Rivers, 174 



Valleys, 108, 252, 282 to 286 inclusive 
Value of Mineral Products, 369 
Vapors or Gases of Volcanoes, 39 



Variations of Temperature, 236, 397, 

398 
Varieties of Coral Formations, 100 
of Earthquake Motion, 52 
of Islands, 90, 95, 96 
of Mineral Substances, 370 
Vegetation, 311 to 338 inclusive, 402 
to 406 inclusive, 408 to 412 in- 
clusive, 428 
Velocity of a River, 168 

of Earthquake Motion, 53 
Venus, 8, 9 

Vertical Distribution of Vegetation, 
324 
Forms of the Land, 82 
Rays of the Sun, 235 
Volcanic Ashes and Cinders, 39, 40, 
242 
Cones, 40 
Dust, 39 
Dykes, 40 
Eruptions, 43 
Vapors or Gases, 39 
Islands, 96 
Volcanoes, 36 to 49 inclusive, 79, 96, 
242 

w. 

Water, 4, 79, 146 to 226 inclusive 

as Food, 153 

Hemispheres, 85 
Water-falls, 169 
Water-sheds, 168, 181, 182 
Water-spouts, 259 
Waves, 207, 208, 212 to 216 inclusive, 

218, 401 
Weather Bureau, 401 

Signals, 401 
Western Continent, 83, 88, 104 

Hemisphere, 21, 83 
Whirlpools, 219 
Whirlwinds, 258 
Wind Zones, 246, 276 
Winds, 79, 241 to 261 inclusive 



Year, Astronomical, 27 

Sidereal, 24 

Tropical, 24 
Yellowstone Park, 165, 388 
Yosemite Falls, 169 



Zones, 28, 239, 246, 317 to 323 inclu- 
sive, 395 

of Animal Life, 342, 344, 346, 347, 
348 

of Calm Winds, 246, 273 

of Cold Temperate Vegetation, 
321 

Mathematical, 28 

North Frigid, 28 

Temperate, 28, 395 

of Perennial Rains, 276 

of Polar Vegetation. 323 
Winds, 246,276 

of Rains, 273, 276 

of Sub-Arctic Vegetation, 322 

of Sub-Tropical Vegetation, 319 

of Trade Winds, 246, 274 

of Tropical Vegetation, 318 

of Variable Winds, 246, 276 

of Vegetation, 317 

of Warm Temperate Vegetation, 
320 

of Winds, 246, 276 

Physical, 239, 395 

Polar, 28, 239, 240, 246, 317, 322, 
323, 344 

South Frigid, 28 
Temperate, 28 

Temperate, 28, 239, 317, 320, 321, 
334, 344, 347 

Torrid or Tropical, 28, 239, 240, 
317, 318, 319, 332, 334, 344, 346, 
395 
Zoological Geography, 339 to 355 in- 
clusive 




m&t 4^Mw^^m 





mm 




188m ms m 



